Linux Bash Script Variable as command

Question

I have to create a script on RHEL and was wondering if I am able to save the output of a command as a variable. For example:

4.2.2 Ensure logging is configured (Not Scored) : = OUTPUT (which comes from the command sudo cat /etc/rsyslog.conf)

This is what I have now.

echo " ### 4.2.2 Ensure logging is configured (Not Scored) : ### "
echo " "
echo "Running command: "
echo "#sudo cat /etc/rsyslog.conf"
echo " "

sudo cat /etc/rsyslog.conf

Thank you!

@user14135159 : Please clarify: Do you mean the **standard output** of a comand, or **stdout+stderr**? — user1934428, Sep 23 '21 at 05:57

score 2 · Answer 1 · answered Sep 23 '21 at 05:55

2

variable=$(command)
variable=$(command [option…] argument1 arguments2 …)
variable=$(/path/to/command)

Taken from https://linuxhint.com/bash_command_output_variable/

answered Sep 23 '21 at 05:55

Wolfgang Blessen

900
10
29

`command` is the name of a specific command built into the shell. It should not be used as a standin for other commands. – Charles Duffy Oct 25 '22 at 02:37
@CharlesDuffy What does command do? Simple executing? – Wolfgang Blessen Oct 25 '22 at 08:02
1

By default, it forces an external command to be used instead of an alias or function for a single execution. Add the `-v` option and it behaves like a built-in version of `which`. – Charles Duffy Oct 25 '22 at 11:47

McLeon · Accepted Answer · 2021-09-23T06:09:16.627

2

Here is an example:

MESSAGE=$(echo "Hello!")
echo $MESSAGE
Hello!

Or the old standard:

MESSAGE=`echo "Hello!"`
echo $MESSAGE
Hello!

In your case:

FILE_CONTENT=$(cat /etc/rsyslog.conf)

NOTE!!!: It is very important to not use spaces near equal!

This form is incorrect:

MESSAGE = `echo "Hello!"`
MESSAGE: command not found

edited Sep 23 '21 at 06:09

answered Sep 23 '21 at 06:02

McLeon

66
3

1

It is good to explain that what you are doing (and what the OP is looking for) is called *Command Substitution*. Where the output of a command is substituted in place of the command for assignment to a variable. (I know you know but the OP may not -- always helps if they want to search further). Good note that `$(...)` is preferred over the older `\`...\``. – David C. Rankin Sep 23 '21 at 06:37
Thank you for the explanation! Really appreciate it :) – user14135159 Sep 23 '21 at 06:49
`echo $MESSAGE` is buggy. See [I just assigned a variable, but `echo $variable` shows something different!](https://stackoverflow.com/questions/29378566/i-just-assigned-a-variable-but-echo-variable-shows-something-else) – Charles Duffy Oct 25 '22 at 02:37

Linux Bash Script Variable as command

2 Answers2