fish-shell/doc_src/read.txt

\section read read - read line of input into variables

\subsection read-synopsis Synopsis
\fish{synopsis}
read [OPTIONS] [VARIABLES...]
\endfish

\subsection read-description Description

`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.

The following options are available:

- `-c CMD` or `--command=CMD` sets the initial string in the interactive mode command buffer to `CMD`.

- `-g` or `--global` makes the variables global.

- `-i` or `--silent` makes the characters typed obfuscated. This is useful for reading things like passwords or other sensitive information. Note that in bash the short flag is `-s`. We can't use that due to the existing use as an alias for `--shell`.

- `-l` or `--local` makes the variables local.

- `-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.

- `-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).

- `-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>.

- `-P PROMPT_STR` or `--prompt-str=PROMPT_STR` uses the string as the prompt for the interactive mode. It is equivalent to <code>echo PROMPT_STR</code> and is provided solely to avoid the need to frame the prompt as a command. All special characters in the string are automatically escaped before being passed to the <code>echo</code> command.

- `-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.

- `-s` or `--shell` enables syntax highlighting, tab completions and command termination suitable for entering shellscript code in the interactive mode.

- `-u` or `--unexport` prevents the variables from being exported to child processes (default behaviour).

- `-U` or `--universal` causes the specified shell variable to be made universal.

- `-x` or `--export` exports the variables to child processes.

- `-a` or `--array` stores the result as an array in a single variable.

- `-z` or `--null` reads up to NUL instead of newline. Disables interactive mode.

`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.

If `-a` or `--array` is provided, only one variable name is allowed and the tokens are stored as an array in this variable.

See the documentation for `set` for more details on the scoping rules for variables.

When read reaches the end-of-file (EOF) instead of the separator, it sets `$status` to 1. If not, it sets it to 0.

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.

\subsection read-example Example

The following code stores the value 'hello' in the shell variable `$foo`.

\fish
echo hello|read foo

# This is a neat way to handle command output by-line:
printf '%s\n' line1 line2 line3 line4 | while read -l foo
                  echo "This is another line: $foo"
              end
\endfish
Add subdirectories darcs-hash:20050920133155-ac50b-9a14c6c664dd03afbe8e15e7c7998fcfb5c3c750.gz 2005-09-20 21:31:55 +08:00			`\section read read - read line of input into variables`

			`\subsection read-synopsis Synopsis`
Simplify styling 2014-08-01 20:25:41 +08:00			`\fish{synopsis}`
Documentation update Rework for Doxygen >1.8. Moved large parts of the documentation to a simplified format, making use of Markdown enhancements and fixing bad long options. 2014-08-01 10:37:32 +08:00			`read [OPTIONS] [VARIABLES...]`
			`\endfish`
Add subdirectories darcs-hash:20050920133155-ac50b-9a14c6c664dd03afbe8e15e7c7998fcfb5c3c750.gz 2005-09-20 21:31:55 +08:00
			`\subsection read-description Description`

put upper bound on data `read` will consume 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 2017-02-08 09:21:35 +08:00			`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.
Add subdirectories darcs-hash:20050920133155-ac50b-9a14c6c664dd03afbe8e15e7c7998fcfb5c3c750.gz 2005-09-20 21:31:55 +08:00
Help cleanup Large list of changes, including formatting and typos for most commands. More substantive changes have been made to alias, bind, block, break, builtin, case, cd, commandline, count, else, emit, fish_config, funced, function, functions, history, math, mimedb, nextd, not, popd, prevd, pushd, pwd, random, read, set, set_color, switch, test, trap, type, ulimit, umask, and while. 2013-05-12 15:56:01 +08:00			`The following options are available:`

Rebase documentation changes 2014-09-03 22:10:53 +08:00			- `-c CMD` or `--command=CMD` sets the initial string in the interactive mode command buffer to `CMD`.

			- `-g` or `--global` makes the variables global.

document new `read --silent` flag 2017-04-12 10:30:12 +08:00			- `-i` or `--silent` makes the characters typed obfuscated. This is useful for reading things like passwords or other sensitive information. Note that in bash the short flag is `-s`. We can't use that due to the existing use as an alias for `--shell`.

Rebase documentation changes 2014-09-03 22:10:53 +08:00			- `-l` or `--local` makes the variables local.

			- `-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.

put upper bound on data `read` will consume 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 2017-02-08 09:21:35 +08:00			- `-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).
Merge branch 'master' into documentation-update Conflicts (fixed): doc_src/design.hdr 2014-09-04 17:00:52 +08:00
Rebase documentation changes 2014-09-03 22:10:53 +08:00			- `-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>.

let `read` take a simple string for the prompt Fixes #802 2017-03-25 23:20:55 +08:00			- `-P PROMPT_STR` or `--prompt-str=PROMPT_STR` uses the string as the prompt for the interactive mode. It is equivalent to <code>echo PROMPT_STR</code> and is provided solely to avoid the need to frame the prompt as a command. All special characters in the string are automatically escaped before being passed to the <code>echo</code> command.

Add --right-prompt flag to read Add a flag to read to allow for setting the right prompt command in addition to the existing support for setting the prompt command. Fixes #1698. 2014-09-22 12:09:21 +08:00			- `-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.

Rebase documentation changes 2014-09-03 22:10:53 +08:00			- `-s` or `--shell` enables syntax highlighting, tab completions and command termination suitable for entering shellscript code in the interactive mode.

			- `-u` or `--unexport` prevents the variables from being exported to child processes (default behaviour).

			- `-U` or `--universal` causes the specified shell variable to be made universal.

			- `-x` or `--export` exports the variables to child processes.

put upper bound on data `read` will consume 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 2017-02-08 09:21:35 +08:00			- `-a` or `--array` stores the result as an array in a single variable.
Rebase documentation changes 2014-09-03 22:10:53 +08:00
Implement new `read --null` flag The `--null` flag to `read` makes it split incoming lines on NUL instead of newlines. This is intended for processing the output of a command that uses NUL separators (such as `find -print0`). Fixes #1694. 2014-09-22 10:18:56 +08:00			- `-z` or `--null` reads up to NUL instead of newline. Disables interactive mode.

Rebase documentation changes 2014-09-03 22:10:53 +08:00			`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.

			If `-a` or `--array` is provided, only one variable name is allowed and the tokens are stored as an array in this variable.
Add subdirectories darcs-hash:20050920133155-ac50b-9a14c6c664dd03afbe8e15e7c7998fcfb5c3c750.gz 2005-09-20 21:31:55 +08:00
Merge branch 'master' into documentation-update Conflicts (fixed): doc_src/design.hdr 2014-09-04 17:00:52 +08:00			See the documentation for `set` for more details on the scoping rules for variables.

put upper bound on data `read` will consume 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 2017-02-08 09:21:35 +08:00			When read reaches the end-of-file (EOF) instead of the separator, it sets `$status` to 1. If not, it sets it to 0.

			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.
Fix documentation on variable scopes for `read` The `read` docs incorrectly asserted that -g was the default for variables. In actuality it behaves the same way that `set` does. 2014-07-14 08:47:44 +08:00
Add subdirectories darcs-hash:20050920133155-ac50b-9a14c6c664dd03afbe8e15e7c7998fcfb5c3c750.gz 2005-09-20 21:31:55 +08:00			`\subsection read-example Example`

Rebase documentation changes 2014-09-03 22:10:53 +08:00			The following code stores the value 'hello' in the shell variable `$foo`.
Add subdirectories darcs-hash:20050920133155-ac50b-9a14c6c664dd03afbe8e15e7c7998fcfb5c3c750.gz 2005-09-20 21:31:55 +08:00
Make line length, wrapping and spacing consistent 2014-08-19 20:41:23 +08:00			`\fish`
			`echo hello\|read foo`
Add while-read example to read docs 2017-01-07 21:31:05 +08:00
			`# This is a neat way to handle command output by-line:`
			`printf '%s\n' line1 line2 line3 line4 \| while read -l foo`
			`echo "This is another line: $foo"`
			`end`
Make line length, wrapping and spacing consistent 2014-08-19 20:41:23 +08:00			`\endfish`