How to overwrite variable value in linux

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i want to overwrite value of variable s1 from "abc" to ---> [more /home/mohsin/Desktop/system_usage_bash_file | grep TIME | awk 'BEGIN {FS=","} {print $3}']

but when i echo i get "abc" on both echos,means it is not overwritten

What I have tried:

#!/bin/bash
s1="abc"
s2="USED"
echo "before"
echo $s1
s1= more /home/mohsin/Desktop/system_usage_bash_file | grep TIME | awk 'BEGIN {FS=","} {print $3}'
echo "after"
echo $s1

Posted 25-Apr-16 22:13pm

Member 12485314

Updated 16-May-16 7:53am

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Richard MacCutchan · Answer 1 · 2016-04-25T22:19:00

Solution 1

s1= more /home/mohsin/Desktop/system_usage_bash_file | grep TIME | awk 'BEGIN {FS=","} {print $3}'

As far as I remember shell scripts, you need to put the command in back quotes thus:

s1= `more /home/mohsin/Desktop/system_usage_bash_file | grep TIME | awk 'BEGIN {FS=","} {print $3}'`

See the section titled Command Substitution at bash(1): GNU Bourne-Again SHell - Linux man page[^].

Posted 25-Apr-16 22:19pm

Richard MacCutchan

Comments

Member 12485314 26-Apr-16 4:35am

On putting back quotes i got error that command not found

Richard MacCutchan 26-Apr-16 4:42am

Well I don't expect it was more, grep or awk.

Member 12485314 26-Apr-16 4:54am

actually i am moving to file directory [more /home/mohsin/Desktop/system_usage_bash_file] than i am greping time and after that printing some value out of it

Richard MacCutchan 26-Apr-16 5:10am

That makes no sense. The more command types the contents of a file on the console. Type the pipeline at the prompt and see what happens.

Jochen Arndt 26-Apr-16 4:58am

Start entering the first command on the shell and continue by appending the additional commands:

more /home/mohsin/Desktop/system_usage_bash_file
more /home/mohsin/Desktop/system_usage_bash_file | grep TIME

and so on.

Once it is working, copy it to your shell script and use the backticks as suggested by Richard or use the $(command) format.

Валентин Ким · Answer 2 · 2016-05-16T07:53:00

Solution 2

You need to write it that way:

root@server:~# s1="$(echo 5)"
root@vpn-1gb-nyc3-01:~# echo $s1
5

So you'll need to rewrite your code like this:

C#

s1= "$(more /home/mohsin/Desktop/system_usage_bash_file | grep TIME | awk 'BEGIN {FS=","} {print $3}')"

Posted 16-May-16 7:53am

Валентин Ким