read

Store data that you type from the keyboard

$ read [variable]

$ read -a [array]

$ read -n [character_count] [variable]

$ read [_ variable1 _ variable2] <<< "[The surname is Bond]"

$ read -r [variable]

$ read -p "[Enter your input here: ]" [variable]

$ read -s [variable]

$ while read line; do [echo|ls|rm|...] "$line"; done < [/dev/stdin|path/to/file|...]

read [-options] [variable...]

-r
    Raw mode. Backslash escapes are not interpreted.

-d delim
    Use delim as the delimiter character, rather than newline. If empty, read will read until EOF.

-n nchars
    Read at most nchars characters rather than one line.

-p prompt
    Display prompt on standard error before reading input.

-t timeout
    Timeout after timeout seconds. Returns failure if the complete input line is not read within timeout seconds. This option is only available when reading input from a terminal, pipe, or other special file.

-s
    Silent mode. Do not echo input on the terminal. This is useful for reading passwords.

-a array
    Read the words into the array named by array, starting with index 0. Only works if IFS is set.

-e
    Use Readline to obtain the line. (Interactive editing)

variable...
    The variables to which the input fields are assigned. If more words are read than variables supplied, the remaining words are assigned to the last variable.

The read command in Linux is used to read a line from standard input and split it into fields. These fields are then assigned to the specified variables. It's a fundamental tool for creating interactive shell scripts and processing user input.

The command offers various options to customize its behavior, such as setting a timeout, specifying a prompt, reading only a certain number of characters, or hiding the input (e.g., for passwords). Understanding read is essential for anyone working with shell scripting as it allows you to create programs that can interact with the user and react to their input.

When using `read` in a pipe, the variables set by `read` are not available in the parent shell, due to the subshell environment created by the pipe.

The `IFS` variable determines how the input line is split into fields. By default, it includes space, tab, and newline characters. You can modify `IFS` to control how the `read` command splits the input into variables. For example, setting `IFS=:` will split the input based on colons.

The `read` command returns an exit status of 0 if it successfully reads a line of input. It returns a non-zero exit status if an error occurs (e.g., a timeout), or if EOF is encountered before any characters are read.

The `read` command has been a standard part of Unix-like operating systems for many years. Its primary purpose has always been to facilitate user input and create interactive scripts. Over time, enhancements have been added, such as the `-t` (timeout) and `-s` (silent) options, to improve the command's versatility and security.

echo(1), printf(1), getopts(1)