Bash builtin Read

The bash read command is a built-in utility that read text from the standard input.

Bash Read Syntax

The syntax for read command is:

read <options> <arguements>

The read command reads a line from the standard input and split it into fields, assigning each word to an arguement. If there are leftover words, they are assigned to the last arguement.

$ read user_input
this is my text
$ echo $user_input
this is my text
$ read var1 var2 var3
there are 3 arguements
$ echo $var1
there
$ echo $var2
are
$ echo $var3
3 arguements

$REPLY

$REPLY is the default variable used by the read builtin.

$ read
this text will be stored in the variable $REPLY
$ echo $REPLY
this text will be stored in the variable $REPLY

Bash read options

options	description
-a array	assign the words read to sequential indices of the array variable ARRAY, starting at zero
-d delim	continue until the first character of DELIM is read, rather than newline
-e use	Readline to obtain the line
-i text	use TEXT as the initial text for Readline
-n nchars	return after reading NCHARS characters rather than waiting for a newline, but honor a delimiter if fewer than NCHARS characters are read before the delimiter
-N nchars	return only after reading exactly NCHARS characters, unless EOF is encountered or read times out, ignoring any delimiter
-p prompt	output the string PROMPT without a trailing newline before attempting to read
-r	do not allow backslashes to escape any characters
-s	do not echo input coming from a terminal
-t	timeout time out and return failure if a complete line of input is not read within TIMEOUT seconds.
-u fd	read from file descriptor FD instead of the standard input

Prompt

Create interactive prompt with -p.

$ read -p "Enter username:"
Enter username: joe
$

Delimiters

By default, newline end the command. The option -d provide a different delimiter to terminate differently.

$ read -d -
hello world - $

Hidng input

Option -s to hide sensitive information input.

$ read  -p "Enter secret password: " -s password
Enter secret password: $ echo $password
secretpassword
$

Use unset <variable> to remove user input

Character limit

Option -n to set the character limit.

$ read -n 5
12345$

The command exits automatically after the 5 characters.

-N set the character limit while ignoring the delimiter.

Timeout

Set a timeout on read to limit taken to input text.

read -t 2

Arrays

Use array instead of variables to store string.

$ read -a arr <<< "Hello world!"
$ echo ${arr[0]}
Hello
$ echo ${arr[1]}
world!
$