/** \mainpage Fish user documentation \section introduction The friendly interactive shell This is the documentation for \c fish, the friendly interactive shell. \c fish is a user friendly commandline shell intended mostly for interactive use. A shell is a program used to execute other programs. For the latest information on \c fish, please visit the fish homepage. \section syntax Syntax overview Shells like fish are used by giving them commands. Every \c fish command follows the same simple syntax. A command is executed by writing the name of the command followed by any arguments. Example: echo hello world calls the \c echo command. \c echo is a command which will write its arguments to the screen. In the example above, the output will be 'hello world'. Everything in fish is done with commands. There are commands for performing a set of commands multiple times, commands for assigning variables, commands for treating a group of commands as a single command, etc.. And every single command follows the same simple syntax. If you wish to find out more about the echo command used above, read the manual page for the echo command by writing: man echo \c man is a command for displaying a manual page on a given topic. The man command takes the name of the manual page to display as an argument. There are manual pages for almost every command on most computers. There are also manual pages for many other things, such as system libraries and important files. Every program on your computer can be used as a command in \c fish. If the program file is located in one of the directories in the PATH, it is sufficient to type the name of the program to use it. Otherwise the whole filename, including the directory (like \c /home/me/code/checkers/checkers or \c ../checkers) has to be used. Here is a list of some useful commands: - \c cd, change the current directory - \c ls, list files and directories - \c man, display a manual page on the screen - \c mv, move (rename) files - \c cp, copy files - \c open, open files with the default application associated with each filetype - \c less, list the contents of files Commands and parameters are separated by the space character ( ). Every command ends with either a newline (i.e. by pressing the return key) or a semicolon (;). More than one command can be written on the same line by separating them with semicolons. A switch is a very common special type of argument. Switches almost always start with one or more hyphens (-) and alter the way a command operates. For example, the \c ls command usually lists all the files and directories in the current working directory, but by using the \c -l switch, the behaviour of ls is changed to not only display the filename, but also the size, permissions, owner and modification time of each file. Switches differ between commands and are documented in the manual page for each command. Some switches are common to most command though, for example '--help' will usually display a help text, '-i' will often turn on interactive prompting before taking action, while '-f' will turn it off. \subsection quotes Quotes Sometimes features such as parameter expansion and character escapes get in the way. When that happens, the user can write a parameter within quotes, either ' (single quote) or " (double quote). There is one important difference between single quoted and double quoted strings: When using double quoted string, variable expansion still takes place. Other than that, a quoted parameter will not be parameter expanded, may contain spaces, and escape sequences are ignored. The only backslash escape accepted within single quotes is \\', which escapes a single quote and \\\\, which escapes the backslash symbol. The only backslash escapes accepted within double quotes are \\", which escapes a double quote, \\$, which escapes a dollar character, and \\\\, which escapes the backslash symbol. Single quotes have no special meaning withing double quotes and vice versa. Example: rm "cumbersome filename.txt" Will remove the file 'cumbersome filename.txt', while rm cumbersome filename.txt would remove the two files 'cumbersome' and 'filename.txt'. \subsection escapes Escaping characters Some characters can not be written directly on the command line. For these characters, so called escape sequences are provided. These are: - '\\a', escapes the alert character - '\\b', escapes the backspace character - '\\e', escapes the escape character - '\\f', escapes the form feed character - '\\n', escapes a newline character - '\\r', escapes the carriage return character - '\\t', escapes the tab character - '\\v', escapes the vertical tab character - '\\ ', escapes the space character - '\\$', escapes the dollar character - '\\\\', escapes the backslash character - '\\*', escapes the star character - '\\?', escapes the question mark character - '\\~', escapes the tilde character - '\\%', escapes the percent character - '\\#', escapes the hash character - '\\(', escapes the left parenthesis character - '\\)', escapes the right parenthesis character - '\\{', escapes the left curly bracket character - '\\}', escapes the right curly bracket character - '\\[', escapes the left bracket character - '\\]', escapes the right bracket character - '\\\<', escapes the less than character - '\\\>', escapes the more than character - '\\^', escapes the circumflex character - '\\xxx', where xx is a hexadecimal number, escapes the ascii character with the specified value - '\\Xxx', where xx is a hexadecimal number, escapes a byte of data with the specified value. If you are using a mutibyte encoding, this can be used to enter invalid strings. Only use this if you know what you are doing. - '\\ooo', where ooo is an octal number, escapes the ascii character with the specified value - '\\uxxxx', where xxxx is a hexadecimal number, escapes the 16-bit unicode character with the specified value - '\\Uxxxxxxxx', where xxxxxxxx is a hexadecimal number, escapes the 32-bit unicode character with the specified value \subsection redirects IO redirection Most program use three types of input/output (IO), each represented by a number called a file descriptor (FD). These are: - Standard input, FD 0, for reading, defaults to reading from the keyboard. - Standard output, FD 1, for writing, defaults to writing to the screen. - Standard error, FD 2, for writing errors and warnings, defaults to writing to the screen. The reason for providing for two output file descriptors is to allow separation of errors and warnings from regular program output. Any file descriptor can be directed to a different output than its default through a simple mechanism called a redirection. An example of a file redirection is echo hello \>output.txt, which directs the output of the echo command to the file error.txt. - To redirect standard input, write \ - To redirect standard output, write \>DESTINATION - To redirect standard error, write ^DESTINATION - To redirect standard output to a file which will be appended, write \>\>DESTINATION_FILE - To redirect standard error to a file which will be appended, write ^^DESTINATION_FILE DESTINATION can be one of the following: - A filename. The output will be written to the specified file. - An ampersand (\&) followed by the number of another file descriptor. The file descriptor will be a duplicate of the specified file descriptor. - An ampersand followed by a minus sign (\&-). The file descriptor will be closed. Example: To redirect both standard output and standard error to the file all_output.txt, you can write echo Hello \>all_output.txt ^\&1. Any FD can be redirected in an arbitrary way by prefixing the redirection with the number of the FD. - To redirect input of FD number N, write N\ - To redirect output of FD number N, write N\>DESTINATION - To redirect output of FD number N to a file which will be appended, write N\>\>DESTINATION_FILE Example: echo Hello 2\>- and echo Hello ^- are equivalent. \subsection piping Piping The user can string together multiple commands into a so called pipeline. This means that the standard output of one command will be read in as standard input into the next command. This is done by separating the commands by the pipe character (|). For example cat foo.txt | head will call the 'cat' program with the parameter 'foo.txt', which will print the contents of the file 'foo.txt'. The contents of foo.txt will then be filtered through the program 'head', which will pass on the first ten lines of the file to the screen. For more information on how to combine commands through pipes, read the manual pages of the commands you want to use using the 'man' command. If you want to find out more about the 'cat' program, type man cat. Pipes usually connect file descriptor 1 (standard output) of the first process to file descriptor 0 (standard input) of the second process. It is possible use a different output file descriptor by prepending the desired FD number and then output redirect symbol to the pipe. For example: make fish 2>|less will attempt to build the fish program, and any errors will be shown using the less pager. \subsection syntax-background Background jobs When you start a job in \c fish, \c fish itself will pause, and give control of the terminal to the program just started. Sometimes, you want to continue using the commandline, and have the job run in the background. To create a background job, append a \& (ampersand) to your command. This will tell fish to run the job in the background. Background jobs are very useful when running programs that have a graphical user interface. Example: emacs \& will start the emacs text editor in the background. \subsection syntax-job-control Job control Most programs allow you to suspend the programs execution and return control to \c fish by Pressing ^Z (Press and hold the Control key and press 'z'). Once back at the \c fish commandline, you can start other programs and do anything you want. If you then want to go back to the suspended command by using the fg command. If you instead want to put a suspended job into the background, use the bg command. To get a listing of all currently started jobs, use the jobs command. \subsection syntax-function Shellscript functions Functions are used to group together commands and arguments using a single name. It can also be used to start a specific command with additional arguments. For example, the following is a function definition that calls the command 'ls -l' to print a detailed listing of the contents of the current directory: 
function ll
	ls -l $argv
end
The first line tells fish that a function by the name of ll is to be defined. To use it, simply write ll on the commandline. The second line tells fish that the command ls -l $argv should be called when ll is invoked. $argv is an array variable, which always contains all arguments sent to the function. In the example above, these are simply passed on to the ls command. For more information on functions, see the documentation for the function builtin. \subsubsection Autoloading functions Functions can be defined on the commandline or in a configuration file, but they can also be automatically loaded. This method of defining functions has several advantages. An autoloaded function becomes avaialble automatically to all running shells, if the function definition is changed, all running shells will automatically reload the altered version, startup time and memory usage is improved, etc. Fish automatically searches through any directories in the array variable \$fish_function_path, and any functions defined are automatically loaded when needed. A function definition file must have a filename consisting of the name of the function plus the suffix '.fish'. The default value for \$fish_function_path is \c ~/.config/fish/functions \c /etc/fish/functions \c /usr/share/fish/functions. The exact path to the last two of these may be slighly different depending on what install path prefix was chosen at configuration time. The rationale behind having three different directories is that the first one is for user specific functions, the second one is for system-wide additional functions and the last one is for default fish functions. The path list is searched in order, meaning that by default, the system administrator can override default fish functions, and the user can override functions defined by the system administrator. It is very important that function definition files only contain the definition for the specified function and nothing else, otherwise it is possible that autoloading a function files requires that the function already be loaded, i.e. a circular dependency. \subsection syntax-words Some common words This is a short explanation of some of the commonly used words in fish. - argument, a parameter given to a command - builtin, a command that is implemented in the shell. Builtins are commands that are so closely tied to the shell that it is impossible to implement them as external commands. - command, a program that the shell can run. - function, a block of commands and arguments that can be called as if they where a single command. By using functions, it is possible to string together multiple smaller commands into one more advanced command. - job, a running pipeline or command - pipeline, a set of commands stringed together so that the output of one command is the input of the next command - redirection, a operation that changes one of the input/output streams associated with a job - switch, a special flag sent as an argument to a command that will alter the behavious of the command. A switch almost always begins with one or two hyphens. \section help Help \c fish has an extensive help system. Use the help command to obtain help on a specific subject or command. For instance, writing help syntax displays the syntax section of this documentation. Help on a specific builtin can also be obtained with the -h parameter. For instance, to obtain help on the \c fg builtin, either type fg -h or help fg. \section completion Tab completion Tab completion is one of the most time saving features of any modern shell. By tapping the tab key, the user asks \c fish to guess the rest of the command or parameter that the user is currently typing. If \c fish can only find one possible completion, \c fish will write it out. If there is more than one completion, \c fish will write out the longest common prefix that all completions have in common. If all completions differ on the first character, a list of all possible completions is printed. The list features descriptions of the completions and if the list doesn't fit the screen, it is scrollable by using the arrow keys, the page up/page down keys or the space bar. Press any other key will exit the list and insert the pressed key into the command line. These are the general purpose tab completions that \c fish provides: - Completion of commands, both builtins, functions and regular programs. - Completion of environment variable names. - Completion of usernames for tilde expansion. - Completion of filenames, even on strings with wildcards such as '*' and '?'. - Completion of job id, job name and process names for process expansion. \c fish provides a large number of program specific completions. Most of these completions are simple options like the \c -l option for \c ls, but some are more advanced. The latter include: - The programs 'man' and 'whatis' show all installed manual pages as completions. - The 'make' program uses all targets in the Makefile in the current directory as completions. - The 'mount' command uses all mount points specified in fstab as completions. - The 'ssh' command uses all hosts in that are stored in the known_hosts file as completions. (see the ssh documentation for more information) - The 'su' command uses all users on the system as completions. - The \c apt-get, \c rpm and \c yum commands use all installed packages as completions. \subsection completion-own Writing your own completions Specifying your own completions is not complicated. To specify a completion, use the \c complete command. \c complete takes as a parameter the name of the command to specify a completion for. For example, to add a completion for the program \c myprog, one would start the completion command with complete -c myprog .... To provide a list of possible completions for myprog, use the \c -a switch. If \c myprog accepts the arguments start and stop, this can be specified as complete -c myprog -a 'start stop'. The argument to the \c -a switch is always a single string. At completion time, it will be tokenized on spaces and tabs, and variable expansion, command substitution and other forms of parameter expansion will take place. Fish has a special syntax to support specifying switches accepted by a command. The switches \c -s, \c -l and \c -o are used to specify a short switch (single character, such as -l), a gnu style long switch (such as --color) and an old-style long switch (like -shuffle), respectively. If the command 'myprog' has an option '-o' which can also be written as '--output', and which can take an additional value of either 'yes' or 'no', this can be specified by writing: complete -c myprog -s o -l output -a "yes no" There are also special switches for specifying that a switch requires an argument, to disable filename completion, to create completions that are only available in some combinations, etc.. For a complete description of the various switches accepted by the \c complete command, see the documentation for the complete builtin, or write 'complete --help' inside the \c fish shell. For examples of how to write your own complex completions, study the completions in /usr/share/fish/completions. (The exact path depends on your chosen installation prefix and may be slightly different) \subsection completion-path Where to put completions Completions can be defined on the commandline or in a configuration file, but they can also be automatically loaded. Fish automatically searches through any directories in the array variable \$fish_complete_path, and any completions defined are automatically loaded when needed. A completion file must have a filename consisting of the name of the command to complete and the suffix '.fish'. The default value for \$fish_complete_path is ~/.config/fish/completions, /etc/fish/completions and /usr/share/fish/completions. The exact path to the last two of these may be slighly different depending on what install path prefix was chosen at configuration time. If a suitable file is found in one of these directories, it will be automatically loaded and the search will be stopped. The rationale behind having three different directories is that the first one is for user specific completions, the second one is for system-wide completions and the last one is for default fish completions. If you have written new completions for a common Unix command, please consider sharing your work by sending it to the fish mailinglist. \section expand Parameter expansion (Globbing) When an argument for a program is given on the commandline, it undergoes the process of parameter expansion before it is sent on to the command. There are many ways in which the user can specify a parameter to be expanded. These include: \subsection expand-wildcard Wildcards If a star (*) or a question mark (?) is present in the parameter, \c fish attempts to match the given parameter to any files in such a way that '?' can match any character except '/' and '*' can match any string of characters not containing '/'. Example: a* matches any files beginning with an 'a' in the current directory. ??? matches any file in the current directory whose name is exactly three characters long. If no matches are found for a specific wildcard, it will expand into zero arguments, i.e. to nothing. If none of the wildcarded arguments sent to a command result in any matches, the command will not be executed. If this happens when using the shell interactively, a warning will also be printed. \subsection expand-command-substitution Command substitution If a parameter contains a set of parenthesis, the text enclosed by the parenthesis will be interpreted as a list of commands. Om expansion, this list is executed, and substituted by the output. If the output is more than one line long, each line will be expanded to a new parameter. A command substitution will not change the value of the status variable outside of the command substitution. Example: The command echo (basename image.jpg .jpg).png will output 'image.png'. The command for i in *.jpg; convert $i (basename $i .jpg).png; end will convert all Jpeg files in the current directory to the PNG format. \subsection expand-brace Brace expansion A comma separated list of characters enclosed in curly braces will be expanded so each element of the list becomes a new parameter. Example: echo input.{c,h,txt} outputs 'input.c input.h input.txt' The command mv *.{c,h} src/ moves all files with the suffix '.c' or '.h' to the subdirectory src. \subsection expand-variable Variable expansion A dollar sign followed by a string of characters is expanded into the value of the environment variable with the same name. For an introduction to the concept of environment variables, read the Environment variables section. Example: echo \$HOME prints the home directory of the current user. If you wish to combine environment variables with text, you can encase the variables within braces to embed a variable inside running text like echo Konnichiwa {$USER}san, which will print a personalized Japanese greeting. The {$USER}san syntax might need a bit of an elaboration. Posix shells allow you to specify a variable name using '$VARNAME' or '${VARNAME}'. Fish supports the former, and has no support whatsoever for the latter or anything like it. So what is '{$VARNAME}' then? Well, '{WHATEVER}' is brace expansion, identical to that supported by e.g. bash. 'a{b,c}d' -> 'abd acd' works both in bash and on fish. So '{$VARNAME}' is a bracket-expansion with only a single element, i.e. it becomes expanded to '$VARNAME', which will be variable expanded to the value of the variable 'VARNAME'. So you might think that the brackets don't actually do anything, and that is nearly the truth. The snag is that there once along the way was a '}' in there somewhere, and } is not a valid character in a variable name. So anything after the otherwise pointless bracket expansion becomes explicitly NOT a part of the variable name, even if it happens to be a legal variable name character. That's why '{$USER}san' looks for the variable '$USER' and not for the variable '$USERsan'. It's simply a case of one syntax lending itself nicely to solving an unrelated problem in its spare time. Variable expansion is the only type of expansion performed on double quoted strings. There is, however, an important difference in how variables are expanded when quoted and when unquoted. An unquoted variable expansion will result in a variable number of arguments. For example, if the variable $foo has zero elements or is undefined, the argument $foo will expand to zero elements. If the variable $foo is an array of five elements, the argument $foo will expand to five elements. When quoted, like "$foo", a variable expansion will always result in exactly one argument. Undefined variables will expand to the empty string, and array variables will be concatenated using the space character. There is one further notable feature of fish variable expansion. Consider the following code snippet: 
set foo a b c
set a 10; set b 20; set c 30
for i in (seq (count $$foo))
	echo $$foo[$i]
end
# Output is:
# 10
# 20
# 30
The above code demonstrates how to use multiple '$' symbols to expand the value of a variable as a variable name. One can simply think of the $-symbol as a variable dereference operator. When using this feature together with array brackets, the brackets will always match the innermost $ dereference. Thus, $$foo[5] will always mean the fift element of the foo variable should be dereferenced and never that the fift element of the doubly dereferenced variable foo. The latter can instead be expressed as $$foo[1][5]. \subsection expand-home Home directory expansion The ~ (tilde) character at the beginning of a parameter, followed by a username, is expanded into the home directory of the specified user. A lone ~, or a ~ followed by a slash, is expanded into the home directory of the process owner. \subsection expand-process Process expansion The \% (percent) character at the beginning of a parameter followed by a string is expanded into a process id. The following expansions are performed: - If the string is the entire word \c self, the shells pid is the result - Otherwise, if the string is the id of a job, the result is the process group id of the job. - Otherwise, if any child processes match the specified string, their pids are the result of the expansion. - Otherwise, if any processes owned by the user match the specified string, their pids are the result of the expansion. This form of expansion is useful for commands like kill and fg, which take the process ids as an argument. Example: fg \%ema will search for a process whose command line begins with the letters 'ema', such as emacs, and if found, put it in the foreground. kill -s SIGINT \%3 will send the SIGINT signal to the job with job id 3. \subsection combine Combining different expansions All of the above expansions can be combined. If several expansions result in more than one parameter, all possible combinations are created. Example: If the current directory contains the files 'foo' and 'bar', the command echo a(ls){1,2,3} will output 'abar1 abar2 abar3 afoo1 afoo2 afoo3'. \section variables Environment variables The concept of environment variables are central to any shell. Environment variables are variables, whose values can be set and used by the user. For information on how to use the current value of a variable, see the section on variable expansion. To set a variable value, use the \c set command. Example: To set the variable \c smurf to the value \c blue, use the command set smurf blue. After a variable has been set, you can use the value of a variable in the shell through variable expansion. Example: To use the value of a the variable \c smurf, write $ (dollar symbol) followed by the name of the variable, like echo Smurfs are $smurf, which would print the result 'Smurfs are blue'. \subsection variables-scope Variable scope There are three kinds of variables in fish, universal, global and local variables. Universal variables are shared between all fish sessions a user is running on one computer. Global variables are specific to the current fish session, but are not associated with any specific block scope, and will never be erased unless the user explicitly requests it using set -e. Local variables are specific to the current fish session, and associated with a specific block of commands, and is automatically erased when a specific block goes out of scope. A block of commands is a series of commands that begins with one of the commands \c 'for, \c 'while' , \c 'if', \c 'function', \c 'begin' or \c 'switch', and ends with the command \c 'end'. The user can specify that a variable should have either global or local scope using the \c -g/--global or \c -l/--local switches. Variables can be explicitly set to be universal with the \c -U or \c --universal switch, global with the \c -g or \c --global switch, or local with the \c -l or \c --local switch. The scoping rules when creating or updating a variable are: -# If a variable is explicitly set to either universal, global or local, that setting will be honored. If a variable of the same name exists in a different scope, that variable will not be changed. -# If a variable is not explicitly set to be either universal, global or local, but has been previously defined, the variable scope is not changed. -# If a variable is not explicitly set to be either universal, global or local and has never before been defined, the variable will be local to the currently executing functions. If no function is executing, the variable will be global. There may be many variables with the same name, but different scopes. When using a variable, the variable scope will be searched from the inside out, i.e. a local variable will be used rather than a global variable with the same name, a global variable will be used rather than a universal variable with the same name. Example: The following code will not output anything: 
begin
	# This is a nice local scope where all variables will die
	set -l pirate 'There be treasure in them thar hills'
end

# This will not output anything, since the pirate was local
echo $pirate
\subsection variables-universal More on universal variables Universal variables are variables that are shared between all the users fish sessions on the computer. Fish stores many of its configuration options as universal variables. This means that in order to change fish settings, all you have to do is change the variable value once, and it will be automatically updated for all sessions, and preserved across computer reboots and login/logout. To see universal variables in action, start two fish sessions side by side, and issue the following command in one of them set fish_color_cwd blue. Since \c fish_color_cwd is a universal variable, the color of the current working directory listing in the prompt will instantly change to blue on both terminals. \subsection variables-functions Variable scope for functions When calling a function, all non-global variables temporarily disappear. This shadowing of the local scope is needed since the variable namespace would become cluttered, making it very easy to accidentally overwrite variables from another function. For example, the following code will output 'Avast, mateys': 
function shiver
	set phrase 'Shiver me timbers'
end

function avast
	set phrase 'Avast, mateys'

	# Calling the shiver function here can not change any variables
	# in the local scope
	shiver

	echo $phrase
end

avast
\subsection variables-export Exporting variables Variables in fish can be exported. This means the variable will be inherited by any commands started by fish. It is convention that exported variables are in uppercase and unexported variables are in lowercase. Variables can be explicitly set to be exported with the \c -x or \c --export switch, or not exported with the \c -u or \c --unexport switch. The exporting rules when creating or updating a variable are identical to the scoping rules for variables: -# If a variable is explicitly set to either be exported or not exported, that setting will be honored. -# If a variable is not explicitly set to be exported or not exported, but has been previously defined, the previous exporting rule for the variable is kept. -# If a variable is not explicitly set to be either global or local and has never before been defined, the variable will not be exported. \subsection variables-arrays Arrays \c fish can store a list of multiple strings inside of a variable. To access one element of an array, use the index of the element inside of square brackets, like this: 
echo $PATH[3]
Note that array indices start at 1 in fish, not 0, as is more common in other languages. This is because many common unix tools like seq are more suited to such use. If you do not use any brackets, all the elements of the array will be written as separate items. This means you can easily iterate over an array using this syntax: 
for i in $PATH; echo $i is in the path; end
To create a variable \c smurf, containing the items \c blue and \c small, simply write: 
set smurf blue small
It is also possible to set or erase individual elements of an array: 
\#Set smurf to be an array with the elements 'blue' and 'small'
set smurf blue small

\#Change the second element of smurf to 'evil'
set smurf[2] evil

\#Erase the first element
set -e smurf[1]

\#Output 'evil'
echo $smurf
If you specify a negative index when expanding or assigning to an array variable, the index will be calculated from the end of the array. For example, the index -1 means the last index of an array. \subsection variables-special Special variables The user can change the settings of \c fish by changing the values of certain environment variables. - \c BROWSER, which is the users preferred web browser. If this variable is set, fish will use the specified browser instead of the system default browser to display the fish documentation. - \c CDPATH, which is an array of directories in which to search for the new directory for the \c cd builtin. - A large number of variable starting with the prefixes \c fish_color and \c fish_pager_color. See Variables for changing highlighting colors for more information. - \c fish_greeting, which is the greeting message printed on startup. - \c LANG, \c LC_ALL, \c LC_COLLATE, \c LC_CTYPE, \c LC_MESSAGES, \c LC_MONETARY, \c LC_NUMERIC and \c LC_TIME set the language option for the shell and subprograms. See the section Locale variables for more information. - \c PATH, which is an array of directories in which to search for commands - \c umask, which is the current file creation mask. The preferred way to change the umask variable is through the umask shellscript function. An attempt to set umask to an invalid value will always fail. \c fish also sends additional information to the user through the values of certain environment variables. The user can not change the values of most of these variables. - \c _, which is the name of the currently running command. - \c argv, which is an array of arguments to the shell or function. \c argv is only defined when inside a function call, or if fish was invoked with a list of arguments, like 'fish myscript.fish foo bar'. This variable can be changed by the user. - \c history, which is an array containing the last commands that where entered. - \c HOME, which is the users home directory. This variable can only be changed by the root user. - \c PWD, which is the current working directory. - \c status, which is the exit status of the last foreground job to exit. - \c USER, which is the username. This variable can only be changed by the root user. Variables whose name are in uppercase are exported to the commands started by fish, those in lowercase are not exported. This rule is not enforced by fish, but it is good coding practice to use casing to distinguish between exported and unexported variables. \c fish also uses several variables internally. Such variables are prefixed with the string __FISH or __fish. These should be ignored by the user. \subsection variables-status The status variable Whenever a process exits, an exit status is returned to the program that started it. This exit status is an integer number, which tells the calling application how the execution of the command went. In general, a zero exit status means that the command executed without problem, but a non-zero exit status means there was some form of problem. Fish stores the exit status of the last process in the last job to exit in the \c status variable. If fish encounters a problem while executing a command, the status variable may also be set to a specific value: - 1 is the generally the exit status from fish builtins if they where supplied with invalid arguments - 125 means an unknown error occured while trying to execute the command - 126 means that the command was not executed because none of the wildcards in the command produced any matches - 127 means that no command with the given name could be located \subsection variables-color Variables for changing highlighting colors The colors used by fish for syntax highlighting can be configured by changing the values of a various variables. The value of these variables can be one of the colors accepted by the set_color command. The \c --bold or \c -b switches accepted by \c set_color are also accepted. The following variables are available to change the highligting colors in fish: - \c fish_color_normal, the default color - \c fish_color_command, the color for commands - \c fish_color_quote, the color for quoted blocks of text - \c fish_color_redirection, the color for IO redirections - \c fish_color_end, the color for process separators like ';' and '&' - \c fish_color_error, the color used to highlight potential errors - \c fish_color_param, the color for regular command parameters - \c fish_color_comment, the color used for code comments - \c fish_color_match, the color used to highlight matching parenthesis - \c fish_color_search_match, the color used to highlight history search matches - \c fish_color_operator, the color for parameter expansion operators like '*' and '~' - \c fish_color_escape, the color used to highlight character escapes like '\\n' and '\\x70' - \c fish_color_cwd, the color used for the current working directory in the default prompt Additionally, the following variables are available to change the highlighting in the completion pager: - \c fish_pager_color_prefix, the color of the prefix string, i.e. the string that is to be completed - \c fish_pager_color_completion, the color of the completion itself - \c fish_pager_color_description, the color of the completion description - \c fish_pager_color_progress, the color of the progress bar at the bottom left corner Example: To make errors highlighted and red, use: set fish_color_error red --bold \subsection variables-locale Locale variables The most common way to set the locale to use a command like 'set -x LANG en_GB.utf8', which sets the current locale to be the english language, as used in Great Britain, using the UTF-8 character set. For a list of available locales, use 'locale -a'. \c LANG, \c LC_ALL, \c LC_COLLATE, \c LC_CTYPE, \c LC_MESSAGES, \c LC_MONETARY, \c LC_NUMERIC and LC_TIME set the language option for the shell and subprograms. These variables work as follows: \c LC_ALL forces all the aspects of the locale to the specified value. If LC_ALL is set, all other locale variables will be ignored. The other LC_ variables set the specified aspect of the locale information. LANG is a fallback value, it will be used if none of the LC_ variables are specified. \section builtin-overview Builtins Many other shells have a large library of builtin commands. Most of these commands are also available as standalone commands, but have been implemented in the shell anyway for whatever reason. To avoid code duplication, and to avoid the confusion of subtly differing versions of the same command, \c fish only implements builtins for actions which cannot be performed by a regular command. \section bundle Commands bundled with fish The following commands are distributed with fish. Many of them are builtins or shellscript functions, and can only be used inside fish. - ., read and execute the commands in a file - and, execute command if previous command suceeded - bg, set a command to the background - begin, execute a block of commands - bind, change keyboard bindings - break, stop the execution of a loop - block, Temporarily block delivery of events - builtin, execute a builtin command - case, conditionally execute a block of commands - cd, change the current directory - command, execute an external program - commandline, set or get the contents of the commandline buffer - complete, add and remove completions - continue, skip the rest of the current lap of a loop - count, count the number of arguments - dirh, view the directory history - dirs, view the directory stack - end, end a block of commands - else, conditionally execute a block of commands - eval, evaluate a string as a command - exec, replace the current process image with a new command - exit, causes \c fish to quit - fg, set a command to the foreground - fishd, the universal variable daemon - for, perform a block of commands once for every element in a list - function, define a new function - functions, print or erase functions - help, show the fish documentation - if, conditionally execute a block of commands - jobs, print the currently running jobs - mimedb, view mimedata about a file - nextd, move forward in the directory history - not, negates the exit status of any command - or, execute a command if previous command failed - popd, move to the topmost directory on the directory stack - prevd, move backwards in the direcotry stack - pushd, push the surrent directory onto the directory stack - random, calculate a pseudo-random number - return, return from a function - read, read from a stream into an environment variable - set, set environment variables - set_color, change the terminal colors - switch, conditionally execute a block of commands - tokenize, split a string up into multiple tokens - ulimit, set or get the shells resurce usage limits - umask, set or get the file creation mask - while, perform a block of commands while a condition is met For more information about these commands, use the --help option of the command to display a longer explanation. \section editor Command Line editor The \c fish editor features copy and paste, a searchable history and many editor functions that can be bound to special keyboard shortcuts. The most important keybinding is probably the tab key, which is bound to the complete function. Here are some of the commands available in the editor: - Tab completes the current token - Home or Ctrl-a moves to the beginning of the line - End or Ctrl-e moves to the end of line - Left and right moves one character left or right - Alt-left and Alt-right moves one word left or right, or moves forward/backward in the directory history if the commandline is empty - Up and down search the command history for the previous/next command containing the string that was specified on the commandline before the search was started. If the commandline was empty when the search started, all commands match. See the history section for more information on history searching. - Alt-up and Alt-down search the command history for the previous/next token containing the token under the cursor before the search was started. If the commandline was not on a token when the search started, all tokens match. See the history section for more information on history searching. - Delete and backspace removes one character forwards or backwards - Ctrl-c delete entire line - Ctrl-d delete one character to the right of the cursor, unless the buffer is empty, in which case the shell will exit - Ctrl-k move contents from the cursor to the end of line to the killring - Ctrl-u move contents from the beginning of line to the cursor to the killring - Ctrl-l clear and repaint screen - Ctrl-w move previous word to the killring - Alt-d move next word to the killring - Alt-w prints a short description of the command under the cursor - Alt-l lists the contents of the current directory, unless the cursor is over a directory argument, in which case the contents of that directory will be listed - Alt-p adds the string '| less;' to the end of the job under the cursor. The result is that the output of the command will be paged. You can change these key bindings by making an inputrc file. To do this, copy the file /etc/fish/fish_inputrc to your home directory and rename it to '.config/fish/fish_inputrc'. Now you can edit the file to change your key bindings. The fileformat of this file is described in the manual page for readline. Use the command man readline to read up on this syntax. Please note that the list of key binding functions in fish is different to that offered by readline. Currently, the following functions are available: - \c backward-char, moves one character to the left - \c backward-delete-char, deletes one character of input to the left of the cursor - \c backward-kill-line, move everything from the beginning of the line to the cursor to the killring - \c backward-kill-word, move the word to the left of the cursor to the killring - \c backward-word, move one word to the left - \c beginning-of-history, move to the beginning of the history - \c beginning-of-line, move to the beginning of the line - \c complete, guess the remainder of the current token - \c delete-char, delete one character to the right of the cursor - \c delete-line, delete the entire line - \c dump-functions, print a list of all key-bindings - \c end-of-history, move to the end of the history - \c end-of-line, move to the end of the line - \c explain, print a description of possible problems with the current command - \c forward-char, move one character to the right - \c forward-word, move one word to the right - \c history-search-backward, search the history for the previous match - \c history-search-forward, search the history for the next match - \c kill-line, move everything from the cursor to the end of the line to the killring - \c kill-whole-line, move the line to the killring - \c kill-word, move the next word to the killring - \c yank, insert the latest entry of the killring into the buffer - \c yank-pop, rotate to the previous entry of the killring You can also bind a pice of shellscript to a key using the same syntax. For example, the Alt-p functionality described above is implemented using the following keybinding. 
"\M-p": if commandline -j|grep -v 'less *$' >/dev/null; commandline -aj "|less;"; end
\subsection killring Copy and paste (Kill Ring) \c fish uses an Emacs style kill ring for copy and paste functionality. Use Ctrl-K to cut from the current cursor position to the end of the line. The string that is cut (a.k.a. killed) is inserted into a linked list of kills, called the kill ring. To paste the latest value from the kill ring use Ctrl-Y. After pasting, use Meta-Y to rotate to the previous kill. If the environment variable DISPLAY is set, \c fish will try to connect to the X-windows server specified by this variable, and use the clipboard on the X server for copying and pasting. \subsection history Searchable history After a command has been entered, it is inserted at the end of a history list. Any duplicate history items are automatically removed. By pressing the up and down keys, the user can search forwards and backwards in the history. If the current command line is not empty when starting a history search, only the commands containing the string entered into the command line are shown. By pressing Alt-up and Alt-down, a history search is also performed, but instead of searching for a complete commandline, each commandline is tokenized into separate elements just like it would be before execution, and each such token is matched agains the token under the cursor when the search began. History searches can be aborted by pressing the escape key. The history is stored in the file '~/.config/fish/fish_history'. It is automatically read on startup and merged on program exit. Example: To search for previous entries containing the word 'make', type 'make' in the console and press the up key. \section job-control Running multiple programs Normally when \c fish starts a program, this program will be put in the foreground, meaning it will take control of the terminal and \c fish will be stopped until the program finishes. Sometimes this is not desirable. For example, you may wish to start an application with a graphical user interface from the terminal, and then be able to continue using the shell. In such cases, there are several ways in which the user can change fish's behaviour. -# By ending a command with the \& (ampersand) symbol, the user tells \c fish to put the specified command into the background. A background process will be run simultaneous with \c fish. \c fish will retain control of the terminal, so the program will not be able to read from the keyboard. -# By pressing ^Z, the user stops a currently running foreground program and returns control to \c fish. Some programs do not support this feature, or remap it to another key. Gnu emacs uses ^X z to stop running. -# By using the fg and bg builtin commands, the user can send any currently running job into the foreground or background. \section initialization Initialization files On startup, \c fish evaluates the files /usr/share/fish/config.fish (Or /usr/local/fish... if you installed fish in /usr/local), /etc/fish/config.fish (Or ~/etc/fish/... if you installed fish in your home directory) and ~/.config/fish/config.fish (Or any other directory specified by the \$XDG_CONFIG_HOME variable), in that order. The first file should not be directly edited, the second one is meant for systemwide configuration and the last one is meant for user configuration. If you want to run a command only on starting an interactive shell, use the exit status of the command 'status --is-interactive' to determine if the shell is interactive. If you want to run a command only when using a login shell, use 'status --is-login' instead. Examples: If you want to add the directory ~/linux/bin to your PATH variable when using a login shell, add the following to your ~/.config/fish/config.fish file: 
if status --is-login
	set PATH $PATH ~/linux/bin
end
If you want to run a set of commands when \c fish exits, use an event handler that is triggered by the exit of the shell: 
function on_exit --on-process \%self
	echo fish is now exiting
end
Universal variables are stored in the file .config/fish/fishd.HOSTNAME, where HOSTNAME is the name of your computer. Do not edit this file directly, edit them through fish scripts or by using fish interactively instead. \section other Other features \subsection color Syntax highlighting \c fish interprets the command line as it is typed and uses syntax highlighting to provide feedback to the user. The most important feedback is the detection of potential errors. By default, errors are marked red. Detected errors include: - Non existing commands. - Reading from or appending to a non existing file. - Incorrect use of output redirects - Mismatched parenthesis When the cursor is over a parenthesis or a quote, \c fish also highlights its matching quote or parenthesis. To customize the syntax highlighting, you can set the environment variables \c fish_color_normal, \c fish_color_command, \c fish_color_substitution, \c fish_color_redirection, \c fish_color_end, \c fish_color_error, \c fish_color_param, \c fish_color_comment, \c fish_color_match, \c fish_color_search_match, \c fish_color_cwd, \c fish_pager_color_prefix, \c fish_pager_color_completion, \c fish_pager_color_description and \c fish_pager_color_progress. Usually, the value of these variables will be one of \c black, \c red, \c green, \c brown, \c yellow, \c blue, \c magenta, \c purple, \c cyan, \c white or \c normal, but they can be an array containing any color options for the set_color command. Issuing set fish_color_error black --background=red --bold will make all commandline errors be written in a black, bold font, with a red background. \subsection prompt Programmable prompt By defining the \c fish_prompt function, the user can choose a custom prompt. The \c fish_prompt function is executed and the output is used as a prompt. Example:

The default \c fish prompt is 

function fish_prompt -d "Write out the prompt"
	printf '\%s\@\%s\%s\%s\%s> ' (whoami) (hostname|cut -d . -f 1) (set_color \$fish_color_cwd) (prompt_pwd) (set_color normal)
end
where \c prompt_pwd is a shellscript function that displays a condensed version of the current working direcotry.

\subsection title Programmable title When using most virtual terminals, it is possible to set the message displayed in the titlebar of the terminal window. This can be done automatically in fish by defining the \c fish_title function. The \c fish_title function is executed before and after a new command is executed or put into the foreground and the output is used as a titlebar message. The $_ environment variable will always contain the name of the job to be put into the foreground (Or 'fish' if control is returning to the shell) when the fish_prompt function is called. Example:

The default \c fish title is 

function fish_title
	echo $_ ' '
	pwd
end

\subsection event Event handlers When defining a new function in fish, it is possible to make it into an event handler, i.e. a function that is automatically run when a specific event takes place. Events that can trigger a handler currently are: - When a signal is delivered - When a process or job exits - When the value of a variable is updated Example: To specify a signal handler for the WINCH signal, write: 
function --on-signal WINCH my_signal_handler
	echo Got WINCH signal!
end
For more information on how to define new event handlers, see the documentation for the function command. \section issues Common issues with fish If you install fish in your home directory, fish will not work correctly for any other user than yourself. This is because fish needs its initalization files to function properly. To solve this problem, either copy the initialization files to each fish users home directory, or install them in /etc. \section i18n Translating fish to other languages Fish uses the GNU gettext library to implement translation to multiple languages. If fish is not available in your language, please consider making a translation. Currently, only the shell itself can be translated, a future version of fish should also include translated manuals. To make a translation of fish, you will first need the sourcecode, available from the fish homepage. Download the latest version, and then extract it using a command like tar -zxf fish-VERSION.tar.gz. Next, cd into the newly created fish directory using cd fish-VERSION. You will now need to configure the sourcecode using the command ./configure. This step might take a while. Before you continue, you will need to know the ISO 639 language code of the language you are translating to. These codes can be found here. For example, the language code for Uighur is ug. Now you have the sourcecode and it is properly configured. Lets start translating. To do this, first create an empty translation table for the language you wish to translate to by writing make po/[LANGUAGE CODE].po in the fish terminal. For example, if you are translating to Uighur, you should write make po/ug.po. This should create the file po/ug.po, a template translation table containing all the strings that need to be translated. Now you are all set up to translate fish to a new language. Open the newly created .po file in your editor of choice, and start translating. The .po file format is rather simple. It contains pairs of string in a format like: 
msgid "%ls: No suitable job\n"
msgstr ""
The first line is the english string to translate, the second line should contain your translation. For example, in swedish the above might become: 
msgid "%ls: No suitable job\n"
msgstr "%ls: Inget passande jobb\n"
\%s, \%ls, \%d and other tokens beginning with a '\%' are placeholders. These will be replaced by a value by fish at runtime. You must always take care to use exactly the same placeholders in the same order in your translation. (Actually, there are ways to avoid this, but they are too complicated for this short introduction. See the full manual for the printf C function for more information.) Once you have provided a translation for fish, please send it to fish-users@lists.sf.net. \section todo Missing features and bugs \subsection todo-features Missing features - Complete vi-mode key bindings - More completions (for example xterm, vim, konsole, gnome-terminal, dcop, cron, rlogin, rsync, arch, finger, nice, locate, bibtex, aspell, xpdf, compress, wine, xmms, dig, batch, cron, g++, javac, java, gcj, lpr, doxygen, whois, find) - Undo support - Check keybinding commands for output - if nothing has happened, don't repaint to reduce flicker - wait shellscript - Support for the screen clipboard \subsection todo-possible Possible features - Multiline editing - tab completion could use smart casing - Completions could support options beginning with a plus (like xterm +fbx) and options without dashes (like top p) Do we really want to complicate the code additionally for such a small number of programs? - mouse support like zsh has with http://stchaz.free.fr/mouse.zsh installed would be awesome - suggest a completion on unique matches by writing it out in an understated color - With a bit of tweakage, quite a few of the readline key-binding functions could be implemented in shellscript. - Highlight beginning/end of block when moving over a block command - Inclusion guards for the init files to make them evaluate only once, even if the user has installed fish both in /etc and in $HOME - Do not actually load/parse fish_history, only mmap it and use some clever string handling. Should save ~150 kB of memory permanently, but is very hard to implement. - command specific wildcarding (use case * instead of case '*', etc.) - Map variables. (export only the values. When expanding with no key specified, expand to all values.) - Descriptions for variables using 'set -d'. - Parse errors should when possible honor IO redirections - Support for writing strings like /u/l/b/foo and have them expand to /usr/local/bin/foo - perhaps through tab expansion - Autoreload inputrc-file on updates - Right-side prompt - Selectable completions in the pager - Per process output redirection - Reduce the space of the pager by one line to allow the commandline to remain visible. - down-arrow could be used to save the current command to the history. Or give the next command in-sequnce. Or both. - A pretty-printer. - Help messages for builtin should not be compiled into fish, they should be kept in a separate directory - Shellscript functions should be able to show help on the commandline instead of launching a browser - Drop support for inputrc-files. Use shellscripts and the bind builtin. Also, redo the syntax for the bind builtin to something more sane. - History could reload itself when the file is updated. This would need to be done in a clever way to avoid chain reactions \subsection bugs Known bugs - Completion for gcc -\#\#\# option doesn't work. - Suspending and then resuming pipelines containing a builtin is broken. How should this be handled? - screen handling code can't handle tabs in input If you think you have found a bug not described here, please send a report to axel@liljencrantz.se . \subsection issues Known issues Older versions of Doxygen has bugs in the man-page generation which cause the builtin help to render incorrectly. Version 1.2.14 is known to have this problem. */ /** \page design Design document \section design-overview Design document \subsection design-overview Overview This is a description of the design principles that have been used to design fish. The fish design has three high level goals. These are: -# Everything that can be done in other shell languages should be possible to do in fish, though fish may rely on external commands in doing so. -# Fish should be user friendly, but not at the expense of expressiveness. Most tradeoffs between power and ease of use can be avoided with careful design. -# Whenever possible without breaking the above goals, fish should follow the Posix syntax. To achive these high-level goals, the fish design relies on a number of more specific design principles. These are presented below, together with a rationale and a few examples for each. \subsection ortho The law of orthogonality The shell language should have a small set of orthogonal features. Any situation where two features are related but not identical, one of them should be removed, and the other should be made powerful and general enough to handle all common use cases of either feature. Rationale: Related features make the language larger, which makes it harder to learn. It also increases the size of the sourcecode, making the program harder to maintain and update. Examples: - Here documents are too similar to using echo inside of a pipeline. - Subshells, command substitution and process substitution are strongly related. \c fish only supports command substitution, the others can be achived either using a block or the psub shellscript function. - Having both aliases and functions is confusing, especially since both of them have limitations and problems. \c fish functions have none of the drawbacks of either syntax. - The many Posix quoting styles are silly, especially \$''. \subsection sep The law of minimalism The shell should only contain features that cannot be implemented in a reasonable way outside of the shell. A large performance decrease, as well as some program complexity increase is acceptable in order to improve separation. Rationale: A modular project is easier to maintain since smaller programs are far easier to understand than larger ones. A modular project is also more future proof since the modules can be individually replaced. Modularity also decreases the severity of bugs, since there is good hope that a bug, even a serious one, in one module, does not take the whole system down. Examples: - Builtin commands should only be created when it cannot be avoided. \c echo, \c kill, \c printf and \c time are among the commands that fish does not implement internally since they can be provided as external commands. Several other commands that are commonly implemented as builtins and can not be implemented as external commands, including \c type, \c vared, \c pushd and \c popd are implemented as shellscript functions in fish. - Mathematical calculations, regex matching, generating lists of numbers and many other funtions can easily be done in external programs. They should not be supported internally by the shell. The law of minimalism does not imply that a large feature set is bad. So long as a feature is not part of the shell itself, but a separate command or at least a shellscript function, bloat is fine. \subsection conf Configurability is the root of all evil Every configuration option in a program is a place where the program is too stupid to figure out for itself what the user really wants, and should be considered a failiure of both the program and the programmer who implemented it. Rationale: Different configuration options are a nightmare to maintain, since the number of potential bugs caused by specific configuration combinations quickly becomes an issue. Configuration options often imply assumptions about the code which change when reimplementing the code, causing issues with backwards compatibility. But mostly, configuration options should be avoided since they simply should not exist, as the program should be smart enough to do what is best, or at least a good enough approximation of it. Examples: - Fish allows the user to set various syntax highlighting colors. This is needed because fish does not know what colors the terminal uses by default, which might make some things unreadable. The proper solution would be for text color preferences to be defined centrally by the user for all programs, and for the terminal emulator to send these color properties to fish. - Fish does not allow you to set the history filename, the number of history entries, different language substyles or any number of other common shell configuration options. A special note on the evils of configurability is the long list of very useful features found in some shells, that are not turned on by default. Both zsh and bash support command specific completions, but no such completions are shipped with bash by default, and they are turned of by default in zsh. Other features that zsh support that are disabled by default include tab-completion of strings containing wildcards, a sane completion pager and a history file. \subsection user The law of user focus When designing a program, one should first think about how to make a intuitive and powerful program. Implementation issues should only be considered once a user interface has been designed. Rationale: This design rule is different than the others, since it describes how one should go about designing new features, not what the features should be. The problem with focusing on what can be done, and what is easy to do, is that to much of the implementation is exposed. This means that the user must know a great deal about the underlying system to be able to guess how the shell works, it also means that the language will often be rather low-level. Examples: - There should only be one type of input to the shell, lists of commands. Loops, conditionals and variable assignments are all performed through regular commands. - The differences between builtin commands, shellscript functions and builtin commands should be made as small as possible. Builtins and shellscript functions should have exactly the same types of argument expansion as other commands, should be possible to use in any position in a pipeline, and should support any io redirection. - Instead of forking when performing command substitution to provide a fake variable scope, all fish commands are performed from the same process, and fish instead supports true scoping - All blocks end with the \c end builtin \subsection disc The law of discoverability A program should be designed to make its features as easy as possible to discover for the user. Rationale: A program whose features are discoverable turns a new user into an expert in a shorter span of time, since the user will become an expert on the program simply by using it. The main benefit of a graphical program over a command line-based program is discoverability. In a graphical program, one can discover all the common features by simply looking at the user interface and guessing what the different buttons, menus and other widgets do. The traditional way to discover features in commandline programs is through manual pages. This requires both that the user starts to use a different program, and the she/he then remembers the new information until the next time she/he uses the same program. Examples: - Everything should be tab-completable, and every tab completion should have a description - Every syntax error and error in a builtin command should contain an error message describing what went wrong and a relevant help page. Whenever possible, errors should be flagged red by the syntax highlighter. - The help manual should be easy to read, easily available from the shell, complete and contain many examples - The language should be uniform, so that once the user understands the command/argument syntax, he will know the whole language, and be able to use tab-completion to discover new featues. */ /** \page license Licenses Fish Copyright (C) 2005 Axel Liljencrantz. Fish is released under the GNU General Public License, version 2. The license agreement is included below. Fish contains code under the BSD license, namely versions of the two functions strlcat and strlcpy, modified for use with wide character strings. This code is copyrighted by Todd C. Miller. The license agreement is included below. The XSel command, written and copyrighted by Conrad Parker, is distributed together with, and used by fish. It is released under the MIT license. The license agreement is included below. The xdgmime library, written and copyrighted by Red Hat, Inc, is used by the mimedb command, which is a part of fish. It is released under the LGPL. The license agreement is included below. Fish contains code from the glibc library, namely the wcstok function. This code is licensed under the LGPL. The license agreement is included below.

GNU GENERAL PUBLIC LICENSE

Version 2, June 1991 

Copyright (C) 1989, 1991 Free Software Foundation, Inc.  
59 Temple Place - Suite 330, Boston, MA  02111-1307, USA

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.

Preamble

The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.

Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations.

Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all.

The precise terms and conditions for copying, distribution and modification follow.

TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

0. This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The "Program", below, refers to any such program or work, and a "work based on the Program" means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term "modification".) Each licensee is addressed as "you".

Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does.

1. You may copy and distribute verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program.

You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.

2. You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions:

a) You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change.

b) You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.

c) If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License. (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.)

These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program.

In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.

3. You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following:

a) Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,

b) Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,

c) Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.)

The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.

If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code.

4. You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

5. You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Program or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Program or works based on it.

6. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients' exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License.

7. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all. For example, if a patent license would not permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program.

If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances.

It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.

This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.

8. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.

9. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.

10. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.

NO WARRANTY

11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

License for wcslcat and wcslcpy

\c fish also contains small amounts of code under the BSD license, namely versions of the two functions strlcat and strlcpy, modified for use with wide character strings. This code is copyrighted by Todd C. Miller. Permission to use, copy, modify, and distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies. THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

License for XSel

The XSel command, written and copyrighted by Conrad Parker, is distributed together with \c fish. It is Copyright (C) 2001 Conrad Parker Permission to use, copy, modify, distribute, and sell this software and its documentation for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation. No representations are made about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty.

GNU LESSER GENERAL PUBLIC LICENSE

Version 2.1, February 1999 

Copyright (C) 1991, 1999 Free Software Foundation, Inc.
51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.

[This is the first released version of the Lesser GPL.  It also counts
 as the successor of the GNU Library Public License, version 2, hence
 the version number 2.1.]

Preamble

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TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

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*/ /** \page faq Frequently asked questions - Why does cd, pwd and other fish commands always resolve symlinked directories to their canonical path? - Why does the cd command autocompletion list the subdirectories of my home directory as completions? - I accidentally entered a directory path and fish changed directory. What happened? - The open command doesn't work. - How do I make fish my default shell? - I'm seeing weird output before each prompt when using screen. What's wrong? - How do I change the greeting message?

\section faq-cwd-symlink Why does cd, $PWD and and various fish commands always resolve symlinked directories to their canonical path? For example if ~/images is a symlink to ~/Documents/Images, if I write 'cd images', my prompt will say ~/D/Images, not ~/images. Because it is impossible to consistently keep symlinked directories unresolved. It is indeed possible to do this partially, and many other shells do so. But it was felt there are enough serious corner cases that this is a bad idea. Most such issues have to do with how '..' is handled, and are varitations of the following example: Writing cd images; ls .. given the above directory structure would list the contents of ~/Documents, not of ~, even though using cd .. changes the current direcotry to ~, and the prompt, the pwd builtin and many other directory information sources suggest that the the current directory is ~/images and it's parent is ~. This issue is not possible to fix without either making every single command into a builtin, breaking Unix semantics or implementing kludges in every single command. This issue can also be seen when doing IO redirection. Another related issue is that many programs that operate on recursive directory trees, like the find command, silently ignore symlinked directories. For example, find $PWD -name '*.txt' silently fails in shells that don't resolve symlinked paths.
\section faq-cd-autocomplete Why does the cd command autocompletion list the subdirectories of my home directory as completions? Because they are completions. In fish, if you specify a relative directory to the cd command, i.e. any path that does not start with either './' or '/', the environment variable CDPATH will be examined, and any directories in this path is used as a base direcotry. To disable this feature, write set CDPATH . on the commandline.
\section faq-cd-implicit I accidentally entered a directory path and fish changed directory. What happened? If fish is unable to locate a command with a given name, fish will test if a directory of that name exists. If it does, it is implicitly assumed that you want to change working directory. For example, the fastest way to switch to your home directory is to simply type ~.
\section faq-open The open command doesn't work. The open command uses the mimetype database and the .desktop files used by Gnome and KDE to identify filetypes and default actions. If at least one of these two desktops are installed, but the open command is not working, this probably means that the relevant files are installed in a nonstandard location. Please contact the fish mailing list, and hopefully this can be resolved. \section faq-default How do I make fish my default shell? If you installed fish manually (e.g. by compiling it, not by using a package manager), you first need to add fish to the list of shells by executing the following command (assuming you installed fish in /usr/local) as root: \section faq-titlebar I'm seeing weird output before each prompt when using screen. What's wrong? Quick answer: Run the following command in fish: 
echo function fish_title;end ~/.config/fish/config.fish
Problem solved! The long answer: Fish is trying to set the titlebar message of your terminal. While screen itself supports this feature, your terminal does not. Unfortuntaly, when the underlying terminal doesn't support setting the titlebar, screen simply passes through the escape codes and text to the underlying terminal instead of ignoring them. It is impossible detect and resolve this problem from inside fish since fish has no way of knowing what the underlying terminal type is. For now, the only way to fix this is to unset the titlebar message, as suggested above. Note that fish has a default titlebar message, which will be used if the fish_title function is undefined. So simply unsetting the fish_title function will not work. echo /usr/local/bin/fish >>/etc/shells If you installed a prepackaged version of fish, the package manager should have already done this for you. In order to change your default shell, type: chsh -s /usr/bin/fish You may need to adjust the above path to e.g. /usr/local/bin/fish. You will need to log out and back in again for the change to take effect.
\section faq-greeting How do I change the greeting message? Change the value of the variable fish_greeting. For example, to remove the greeting use: 
set fish_greeting
*/