read - read line of input into variables

Synopsis

read [OPTIONS] [VARIABLE ...]

Description

read reads from standard input and either writes the result back to standard output (for use in command substitution), or stores the result in one or more shell variables. By default, read reads a single line and splits it into variables on spaces or tabs. Alternatively, a null character or a maximum number of characters can be used to terminate the input, and other delimiters can be given. Unlike other shells, there is no default variable (such as REPLY) for storing the result - instead, it is printed on standard output.

The following options are available:

  • -c CMD or --command=CMD sets the initial string in the interactive mode command buffer to CMD.
  • -d DELIMITER or --delimiter=DELIMITER splits on DELIMITER. DELIMITER will be used as an entire string to split on, not a set of characters.
  • -g or --global makes the variables global.
  • -s or --silent masks characters written to the terminal, replacing them with asterisks. This is useful for reading things like passwords or other sensitive information.
  • -l or --local makes the variables local.
  • -n NCHARS or --nchars=NCHARS makes read return after reading NCHARS characters or the end of the line, whichever comes first.
  • -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 set_color green; echo read; set_color normal; echo "> "
  • -P PROMPT_STR or --prompt-str=PROMPT_STR uses the string as the prompt for the interactive mode. It is equivalent to echo PROMPT_STR 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 echo 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. NOTE: Prior to fish 3.0, the short opt for --shell was -s, but it has been changed for compatibility with bash's -s short opt for --silent.
  • -t -or --tokenize causes read to split the input into variables by the shell's tokenization rules. This means it will honor quotes and escaping. This option is of course incompatible with other options to control splitting like --delimiter and does not honor $IFS (like fish's tokenizer). It saves the tokens in the manner they'd be passed to commands on the commandline, so e.g. a\ b is stored as a b. Note that currently it leaves command substitutions intact along with the parentheses.
  • -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 --list stores the result as a list in a single variable. This option is also available as --array for backwards compatibility.
  • -z or --null marks the end of the line with the NUL character, instead of newline. This also disables interactive mode.
  • -L or --line reads each line into successive variables, and stops after each variable has been filled. This cannot be combined with the --delimiter option.

Without the --line option, read reads a single line of input from standard input, breaks it into tokens, 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.

If no option to determine how to split like --delimiter, --line or --tokenize is given, the variable IFS is used as a list of characters to split on. Relying on the use of IFS is deprecated and this behaviour will be removed in future versions. The default value of IFS contains space, tab and newline characters. As a special case, if IFS is set to the empty string, each character of the input is considered a separate token.

With the --line option, read reads a line of input from standard input into each provided variable, stopping when each variable has been filled. The line is not tokenized.

If no variable names are provided, read enters a special case that simply provides redirection from standard input to standard output, useful for command substitution. For instance, the fish shell command below can be used to read data that should be provided via a command line argument from the console instead of hardcoding it in the command itself, allowing the command to both be reused as-is in various contexts with different input values and preventing possibly sensitive text from being included in the shell history:

mysql -uuser -p(read)

When running in this mode, read does not split the input in any way and text is redirected to standard output without any further processing or manipulation.

If -a or --array is provided, only one variable name is allowed and the tokens are stored as a list 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 terminator, the exit status is set to 1. Otherwise, it is set to 0.

In order to protect the shell from consuming too many system resources, read will only consume a maximum of 100 MiB (104857600 bytes); if the terminator is not reached before this limit then VARIABLE is set to empty and the exit status is set to 122. This limit can be altered with the fish_read_limit variable. If set to 0 (zero), the limit is removed.

Using another read history file

The read command supported the -m and --mode-name flags in fish versions prior to 2.7.0 to specify an alternative read history file. Those flags are now deprecated and ignored. Instead, set the fish_history variable to specify a history session ID. That will affect both the read history file and the fish command history file. You can set it to an empty string to specify that no history should be read or written. This is useful for presentations where you do not want possibly private or sensitive history to be exposed to the audience but do want history relevant to the presentation to be available.

Example

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

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

# Delimiters given via "-d" are taken as one string
echo a==b==c | read -d == -l a b c
echo $a # a
echo $b # b
echo $c # c

# --tokenize honors quotes and escaping like the shell's argument passing:
echo 'a\ b' | read -t first second
echo $first # outputs "a b", $second is empty

echo 'a"foo bar"b (command echo wurst)*" "{a,b}' | read -lt -l a b c
echo $a # outputs 'afoo bar' (without the quotes)
echo $b # outputs '(command echo wurst)* {a,b}' (without the quotes)
echo $c # nothing