Bash Assign Output of Shell Command To Variable

Bash Assign Output of Shell Command To And Store To a Variable

To assign output of any shell command to variable in bash, use the following command substitution syntax:

var=$(command-name-here)
var=$(command-name-here arg1)
var=$(/path/to/command)
var=$(/path/to/command arg1 arg2)

OR use backticks based syntax as follows to assign output of a Linux command to a variable:

var=`command-name-here`
var=`command-name-here arg1`
var=`/path/to/command`
var=`/path/to/command arg1 arg2`

Do not put any spaces after the equals sign and command must be on right side of =. See how to assign values to shell variables for more information.

Examples

Let us see some common examples for Linux, macOS, *BSD and Unix-like systems running bash.

BASH command output to the variable

To store date command output to a variable called now, enter:

## store date command output to $now  ##
now=$(date)

OR

## alternate syntax ##
now=`date`

To display back result (or output stored in a variable called $now) use the echo or printf command:

echo "$now"
printf "%s\n" "$now"

Sample outputs:

Wed Apr 25 00:55:45 IST 2012

You can combine the echo command and shell variables as follows:

echo "Today is $now"

Sample outputs:

Today is Wed Apr 25 00:55:45 IST 2012

You can do command substitution in an echo command itself (no need to use shell variable):

echo "Today is $(date)"
printf "Today is %s\n" "$(date)"

Sample outputs:

Today is Wed Apr 25 00:57:58 IST 2011

How to use multiline command

Try the following syntax:
my_var=$(command \
arg1 \
arg2 \
arg3 )
echo "$my_var"
For example,

## date example ##
OUT=$(date \
--date='TZ="America/Los_Angeles" 09:00 next Thu')
echo "$OUT"

Another ping command example for you:

#!/bin/bash
_ping="/bin/ping"
domain="www.cyberciti.biz"
 
ping_avg="$(${_ping} \
-q \
-c 4 \
${domain} | grep rtt)"
 
echo "Avg ping time for ${domain} : ${ping_avg}"

Various ways to assign the output of a command to a shell variable

Conclusion

You learned how to assign output of a Linux and Unix command to a bash shell variable. For more information see GNU bash command man page here and read the following docs:

• Command substitution – from the Linux shell scripting tutorial wiki.
• See man pages: printf(1)