Question

Anyone knows what $? means in BASH?

I have to write a script that restarts a process if it crashes or is killed. So I found this to start from :

RESTART="/etc/init.d/apache2 restart"
if [ $? -ne 0 ] # if apache not running
then
   # restart apache
   $RESTART
fi

I have done a search, but $? eludes me.

I am not sure if the above script is the best way to do this, I am assuming that $RESTART will hang until the process is killed or dies? If not, I would assume there would be some kind of sleep() call in there so this thing doesn;t spin at 1000 miles per hour.

Answer 1

Anyone know what $? means in bash

It’s the exit status of the most recently executed command.

[cnicutar@fresh ~]$ ls /nothing
ls: cannot access /nothing: No such file or directory
[cnicutar@fresh ~]$ echo $?
2

[cnicutar@fresh ~]$ ls -ld .
drwx------ 15 cnicutar users 4096 Aug 16 15:29 .
[cnicutar@fresh ~]$ echo $?
0

Look it up at tldp.