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https://github.com/fish-shell/fish-shell
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af7f5f42b6
This puts a hard upper bound of 10 MiB on the amount of data that read will consume. This is to avoid having the shell consume an unreasonable amount of memory, possibly causing the system to enter a OOM condition, if the user does something non-sensical. Fixes #3712
61 lines
3.4 KiB
Text
61 lines
3.4 KiB
Text
\section read read - read line of input into variables
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\subsection read-synopsis Synopsis
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\fish{synopsis}
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read [OPTIONS] [VARIABLES...]
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\endfish
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\subsection read-description Description
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`read` reads from standard input and stores the result in one or more shell variables. By default it reads one line terminated by a newline but options are available to read up to a null character and to limit each "line" to a maximum number of characters.
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The following options are available:
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- `-c CMD` or `--command=CMD` sets the initial string in the interactive mode command buffer to `CMD`.
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- `-g` or `--global` makes the variables global.
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- `-l` or `--local` makes the variables local.
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- `-m NAME` or `--mode-name=NAME` specifies that the name NAME should be used to save/load the history file. If NAME is fish, the regular fish history will be available.
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- `-n NCHARS` or `--nchars=NCHARS` causes `read` to return after reading NCHARS characters rather than waiting for a complete line of input (either newline or null terminated).
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- `-p PROMPT_CMD` or `--prompt=PROMPT_CMD` uses the output of the shell command `PROMPT_CMD` as the prompt for the interactive mode. The default prompt command is <code>set_color green; echo read; set_color normal; echo "> "</code>.
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- `-R RIGHT_PROMPT_CMD` or `--right-prompt=RIGHT_PROMPT_CMD` uses the output of the shell command `RIGHT_PROMPT_CMD` as the right prompt for the interactive mode. There is no default right prompt command.
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- `-s` or `--shell` enables syntax highlighting, tab completions and command termination suitable for entering shellscript code in the interactive mode.
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- `-u` or `--unexport` prevents the variables from being exported to child processes (default behaviour).
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- `-U` or `--universal` causes the specified shell variable to be made universal.
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- `-x` or `--export` exports the variables to child processes.
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- `-a` or `--array` stores the result as an array in a single variable.
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- `-z` or `--null` reads up to NUL instead of newline. Disables interactive mode.
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`read` reads a single line of input from stdin, breaks it into tokens based on the `IFS` shell variable, and then assigns one token to each variable specified in `VARIABLES`. If there are more tokens than variables, the complete remainder is assigned to the last variable. As a special case, if `IFS` is set to the empty string, each character of the input is considered a separate token.
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If `-a` or `--array` is provided, only one variable name is allowed and the tokens are stored as an array in this variable.
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See the documentation for `set` for more details on the scoping rules for variables.
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When read reaches the end-of-file (EOF) instead of the separator, it sets `$status` to 1. If not, it sets it to 0.
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Fish has a default limit of 10 MiB on the number of characters each `read` will consume. If you attempt to read more than that `$status` is set to 122 and the variable will be empty. You can modify that limit by setting the `FISH_READ_BYTE_LIMIT` variable at any time including in the environment before fish starts running. This is a safety mechanism to keep the shell from consuming an unreasonable amount of memory if the input is malformed.
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\subsection read-example Example
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The following code stores the value 'hello' in the shell variable `$foo`.
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\fish
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echo hello|read foo
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# This is a neat way to handle command output by-line:
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printf '%s\n' line1 line2 line3 line4 | while read -l foo
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echo "This is another line: $foo"
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end
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\endfish
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