Bsrgvty

I need to check if a specific package is installed on a machine from within a Bash script.

I found something like that but I don't know how use it correctly.

dpkg -l | grep "ansible" | awk 'print $2'
if [$? -eq 0]; then
 echo OK
else
 echo FAIL
fi

I need check, if command dpkg -l | grep "ansible" | awk 'print $2' return me word "Ansible" then echo OK, else echo FAIL.

@EDIT

I think better will be command

dpkg -l | grep "ansible" | awk 'print $2'

so this command return me two words:

ansible
ansible_lint

How should I use this bash script? If I doing something like that:

ansible = $?
if [$? -eq 0]; then
 echo OK
else
 echo FAIL
fi

that's not work, but I'm sure I doing that wrong. How can I read result from dpkg -l | grep "ansible" | awk 'print $2' command and if I get word "ansible" script will print OK, if not print FAIL.

You can check if the software is installed on this way:

if [ "$(dpkg -l | awk '/ansible/ print '|wc -l)" -ge 1 ]; then
 echo OK
else
 echo FAIL
fi

You can't use exit code because it will be from awk and in this case always be 0

If you know the exact package name, you can just ask dpkg if it's installed with

dpkg -l packagename

For example:

$ dpkg -l pulsea
dpkg-query: no packages found matching pulsea

The exit code is also 1 (fail) if a package isn't installed, you can test for that (as seen later).

$ dpkg -l pulseaudio
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==================-==============-==============-=========================
ii pulseaudio 10.0-1+deb9u1 i386 PulseAudio sound server

Here the exit code is 0 (success), so you can do this too

$ if dpkg -l pulseaudio; then echo yes;fi
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==================-==============-==============-=========================
ii pulseaudio 10.0-1+deb9u1 i386 PulseAudio sound server
yes

Note the trailing "yes" above. But now since you can just use the exit code, you don't really care about dpkg's output, so ignore it with an if or an && (AND list):

$ if dpkg -l pulseaudio >/dev/null; then echo yes;fi
yes

$ dpkg -l pulseaudio >/dev/null && echo yes
yes

dpkg can also match partial names, using asterisks, like

$ dpkg -l "*pulse*"

About pipes and their exit status, if you want to see if a command somewhere in a pipeline has failed you'll have to do something like examining the $PIPESTATUS[@]:

$ false | true
$ echo $PIPESTATUS[@] 
1 0

And like $?, $PIPESTATUS[@] changes with every command, so if you want to examine them more than once you have to save them to another variable first. In your example

ansible = $?
if [$? -eq 0]; then

$? has already changed by the if test, and it's probably 0 since assigning a variable like that almost always succeeds.

To check, if package named 'pkgname' is successfully installed, use

if dpkg-query -W -f'$db:Status-Abbrevn' pkgname 2>/dev/null 
 | grep -q '^.i $'; then
 echo 'Installed'
else
 echo 'Not installed'
fi

See man dpkg-query about usage of dpkg-query. With -q option grep does not output anything, but exits with code 0 if and only if there is a match.