I want to grep a specific status of a service (tomcat8.service).
Only if the string was found, I want to execute some logic.
Problem: even if I execute the script on service name that does not exist ("asd" in this example), the if $status still matches and prints out. But why?
status = $(systemctl status asd.service | grep 'active')
echo $status
if $status
then
echo "$SERVICE was active"
exit 0
fi
exit 0
Result output is: asd.service was active, which is certainly not true.
The echo $status prints: status: Unknown job: =
2 Answers
You can make use of grep's return status.
systemctl status asd.service | grep 'active' \
&& status=active \
|| status=not_active
if [ "$status" == "active" ]; then
[...]
fi
or even easier:
test $(systemctl status asd.service | grep 'active') \
&& echo "$SERVICE was active"
or if you prefer if:
if $(systemctl status asd.service | grep 'active'); then
echo "$SERVICE was active"
fi
Anyways, take care about the keywords inactive, not active, active (exited) or alike. This will also match your grep statement. See the comments. Thanks @ Terrance for the hint.
Update:
No need for grep. systemctl has the command is-active included.
systemctl -q is-active asd.service \
&& echo "$SERVICE was active"
or:
if systemctl -q is-active asd.service; then
echo "is active";
fi
Some code review comments:
- sh/bash/ksh/zsh variable assignments look like
var=value-- no spaces around the=are allowed. (documentation) status=$(some command)-- the status variable hold the output of the command, not the exit status. The exit status is in the$?variablethe
ifstatement acts on the exit status of the subsequent command (documentation)if some_comment; then action1; else action2; fiMost often, the command is
[or[[to test some condition.However,
grephas a clear exit status: 0 if the pattern was found, 1 otherwise. So you want this:if systemctl status asd.service | grep -q 'active'; then echo "$SERVICE was active" fi
