Ubuntu – Display output of command executed in bash as it is executing

bashscripts

I've got a line in my bash script like this:

echo "`some_command`"

Now, some_command executes for around 1-2mins and it keeps printing alerts/messages in that interval.

Problem is when I execute my bash script, the script has no output for 1-2mins and then directly displays the output after complete execution of some_command.

How can I make my bash script output some_command as it is executing? Is there a way to do so?

Best Answer

xtrace

You could set the xtrace option (commonly used for debugging shell scripts) before running the command (no need to use command substitution). Also, don’t forget to unset the option afterwards.

set -x
some_command
set +x

Example:

$ set -x; sleep 2 && echo fin; set +x
+ sleep 2
+ echo fin
fin
+ set +x

echo

If you find the xtrace output to be too cluttered, you could simply echo the name of the command beforehand:

echo some_command
some_command

Related Solutions

Ubuntu – How to stop the bash script when a condition fails

The problem is that || and && only skip one subsequent stanza of a command chain when the condition fails. If you write out a full block structure it makes perfect sense. What you wrote becomes this:

if ! true ; then
   echo "This shouldn't print"
else
   exit
fi

What you want is this:

if ! true ; then
   echo "This shouldn't print"
   exit
fi

When you are using Bash's shortcut conditional operators it is better to avoid mixing them. The logic is much easier to understand while you're writing it, and your readers will appreciate your good style.

Ubuntu – Bash script with smaller scripts internally

The correct solution for you depends on what you want:

Combining the scripts with && will only execute the second if the first exits successfully
Combining the scripts with || will only execute the second if the first doesn't exit successfully

If you want the second command to be executed after the first no matter whether it exits successfully or not, you can use either ; or & wait:

bash script1.sh ;
bash script2.sh & wait
bash script3.sh