====== BASH - Output - Assign Output of Shell Command To Variable ======

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

<code bash>
var=$(command-name-here)
var=$(command-name-here arg1)
var=$(/path/to/command)
var=$(/path/to/command arg1 arg2)
</code>

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

<code bash>
var=`command-name-here`
var=`command-name-here arg1`
var=`/path/to/command`
var=`/path/to/command arg1 arg2`
</code>

Do not put any spaces after the equals sign and command must be on right side of =. 

<WRAP important>
**NOTE:** The use of **$(command)** is not portable.  This is BASH-only syntax.  If you want portable write using backticks such as "`command`".
</WRAP>


----

===== Examples =====

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

<code bash>
now=$(date)
</code>

or

<code bash>
now=`date`
</code>

----

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

<code bash>
echo "$now"
printf "%s\n" "$now"
</code>

returns:

<code bash>
Wed Apr 25 00:55:45 IST 2012
</code>

----

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

<code bash>
echo "Today is $now"
</code>

returns:

<code bash>
Today is Wed Apr 25 00:55:45 IST 2012
</code>

----

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

<code bash>
echo "Today is $(date)"
printf "Today is %s\n" "$(date)"
</code>

returns:

<code bash>
Today is Wed Apr 25 00:57:58 IST 2011
</code>


----

===== Use Multiline Command =====

Try the following syntax:

<code bash>
my_var=$(command \
arg1 \
arg2 \
arg3 )
echo "$my_var"
</code>

----

===== Example using Date =====

<code bash>
OUT=$(date \
--date='TZ="Europe/Jersey" 09:00 next Thu')
echo "$OUT"
</code>

----

===== Example using Ping =====

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