Bash built-in read: read one line from stdin and assign words to variables
By default, read reads a line from stdin and assigns the read words to variables (but see also the -p option).
echo Enter your name:
read name
echo Your name is $name
The read input is by default split (but see $IFS below):
echo Enter two integers
read a b
echo $a + $b = $(( $a + $b ))
The following example reads and assigns a value to the variable $greeting. Because the read command runs in a new process which is terminated when the pipeline ends, the assigned value will be lost:
echo hello | read greeting
echo $greeting
This «problem» can be avoided by using <<< (a so called here string):
read greeting <<<hello
echo $greeting
The following command assings assigns - to $IFS (the input field separator) and assigns the current year, month and day from ISO 8601 format. Note that month and day will be 2 characters (possibly with a leading zero):
IFS=- read year month day <<<$( date-I )
echo "The year is $year, the month is $month and the day is $day."
Iterate over each line in a file and assign fields to variables:
while IFS=: read username password uid gid fullname home shell; do
echo "Username : $username"
echo "User/Group ID : $uid/$gid"
# echo "Full Name : $fullname"
echo "Home Directory: $home"
echo "Shell : $shell"
echo "--------------------------"
done < /etc/passwd
Options
-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. The value of the TMOUT variable is the default timeout. timeout may be a fractional number. If timeout is 0, read returns immediately, without trying to read any data, returning success only if input is available on the specified file descriptor. The exit status is greater than 128 if the timeout is exceeded
-u fd
read from file descriptor FD instead of the standard input
Press any key to continue
echo "foo bar baz."
#
# Waiting for the user to press any key
# -n 1: one character is enough
# -s : suppress echoing the key that was pressed
# -p : What should be prompted
#
#
read -n 1 -s -p "Press any key to continue"
echo "Continuing..."