Bash: If/Else statement in one line
I am trying to check if a process (assume it is called some_process
) is running on a server. If it is, then echo 1, otherwise echo 0.
This is the command that I am using but it only works partially (more info below). Note that I need to write the script in one line.
ps aux | grep some_proces[s] > /tmp/test.txt && if [ $? -eq 0 ]; then echo 1; else echo 0; fi
Note: The [s]
in some_proces[s]
is to prevent grep
from returning itself.
If some_process
is running, then "1"
gets echoed, which is fine. However, if some_process
is not running, nothing gets echoed.
There is no need to explicitly check $?
. Just do:
ps aux | grep some_proces[s] > /tmp/test.txt && echo 1 || echo 0
Note that this relies on echo not failing, which is certainly not guaranteed. A more reliable way to write this is:
if ps aux | grep some_proces[s] > /tmp/test.txt; then echo 1; else echo 0; fi
&&
means "and if successful"; by placing your if
statement on the right-hand side of it, you ensure that it will only run if grep
returns 0
. To fix it, use ;
instead:
ps aux | grep some_proces[s] > /tmp/test.txt ; if [ $? -eq 0 ]; then echo 1; else echo 0; fi
(or just use a line-break).
Use grep -vc
to ignore grep
in the ps
output and count the lines simultaneously.
if [[ $(ps aux | grep process | grep -vc grep) > 0 ]] ; then echo 1; else echo 0 ; fi