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doc: Document how IFS affects command substitution

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IFS is used for more than just the read builtin. Setting it to the empty
string also disables line-splitting in command substitution, and it's
done this for the past 7 years. Some day we may have a better way to do
this, but for now, document the current solution.
This commit is contained in:
Kevin Ballard 2014-07-13 18:51:54 -07:00 committed by ridiculousfish
parent b9948ca297
commit 20899f2df9
1 changed files with 5 additions and 1 deletions
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doc_src/index.hdr.in
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@ -603,7 +603,7 @@ command. If a parameter contains a set of parenthesis, the text enclosed by the
parenthesis will be interpreted as a list of commands. On expansion, parenthesis will be interpreted as a list of commands. On expansion,
this list is executed, and substituted by the output. If the output is 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 more than one line long, each line will be expanded to a new
parameter. parameter. Setting \c IFS to the empty string will disable line splitting.
The exit status of the last run command substitution is available in the <a The exit status of the last run command substitution is available in the <a
href='#variables-status'>status</a> variable. href='#variables-status'>status</a> variable.
@ -620,6 +620,9 @@ The command <code>for i in *.jpg; convert $i (basename $i .jpg).png;
end</code> will convert all JPEG files in the current directory to the end</code> will convert all JPEG files in the current directory to the
PNG format using the \c convert program. PNG format using the \c convert program.
The command <code>begin; set -l IFS; set data (cat data.txt); end</code>
will set the \c data variable to the contents of 'data.txt' without
splitting it into an array.
\subsection expand-brace Brace expansion \subsection expand-brace Brace expansion
@ -1006,6 +1009,7 @@ values of most of these variables.
- \c argv, 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 argv, 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, an array containing the last commands that were entered. - \c history, an array containing the last commands that were entered.
- \c HOME, the user's home directory. This variable can be changed by the user. - \c HOME, the user's home directory. This variable can be changed by the user.
- \c IFS, the internal field separator that is used for word splitting with the <a href="commands.html#read">read builtin</a>. Setting this to the empty string will also disable line splitting in <a href="#expand-command-substitution">command substitution</a>. This variable can be changed by the user.
- \c PWD, the current working directory. - \c PWD, the current working directory.
- \c status, the <a href="#variables-status">exit status</a> of the last foreground job to exit. If the job was terminated through a signal, the exit status will be 128 plus the signal number. - \c status, the <a href="#variables-status">exit status</a> of the last foreground job to exit. If the job was terminated through a signal, the exit status will be 128 plus the signal number.
- \c USER, the current username. This variable can be changed by the user. - \c USER, the current username. This variable can be changed by the user.