[SOLVED] How do i check if a package manager is running with BASH

[oodlesOfmoodles]

Hey!

I'm writing a script that will automatically do some things for the user. I want, at one point, for the script to install VLC for DVD playback. How do I check to see if a package manger is running so I can create a prompt that tells the user to close out of synaptic or wait until the update-manager is done working.

How would I go about doing this?


Thanks!

[SOULRiDER]

You could check if theres a lock.

[oodlesOfmoodles]

Yea that's what I was thinking, but how do I do that?

[kevykev]

Well the lock file is /var/lib/dpkg/lock. In c you could try to open the file with:



fd = open ("/var/lib/dpkg/lock", O_RDWR | O_CREAT | O_TRUNC, 0640);
if (fd == -1) {
// cant get lock
}
// lock the file .. do work

// unlock and close the file


in bash you might be able to use lsof to see if the file is open



if lsof /var/lib/dpkg/lock >> /dev/null; then
# file is locked
exit 1
fi


Not sure about this tho

[Keith Hedger]

how about
top -bn1| grep apt any output will show that apt or synaptic is runing.

[stroyan]

Strace of synaptic shows that /var/lib/dpkg/lock is used with a lockf (or fcntl F_SETLK) type of lock.
Bash doesn't have any direct way to test a lockf lock. You could use a bit of python to test for the lock. Here is a quick first try-
#!/bin/bash
python << END
import struct, fcntl, os, sys
f = open("/var/lib/dpkg/lock", 'w')
try:
fcntl.lockf(f, fcntl.LOCK_EX|fcntl.LOCK_NB)
except IOError:
sys.exit(1)
sys.exit(0)
END
echo $? You might want to first test for uid equal to root. Otherwise the open will fail. That should have a different user message.

[oodlesOfmoodles]

I just tested kevykev's suggestion and it works perfectly (though i had to add 'sudo' before the 'lsof').

Thanks for all your help! I love this forum.

[Thund3rstruck]

If the following returns an integer greater than 1 then synaptic is running



ps aux | grep -c synaptic

[oodlesOfmoodles]

can you explain what that command does? that would be awesome!


thanks for your help

[stroyan]

ps aux | grep -c synaptic is running ps to print all user commands and their arguments. The a option lists all users.
The u option adds more (unnecessary) fields of information.
The x option includes processes that don't have a controlling terminal.

The output of ps is piped to grep -c which counts the number of lines that contain the string 'synaptic'.
That number is almost always at least one because the grep process itself contains the string in its arguments as printed by ps.
But sometimes grep is not started by the time that ps is done running.
That makes the results inconsistent.

If you really want to use searching for a synaptic process then you would be better served by
pgrep -c synapticThe pgrep command looks at only the process name and not the arguments passed to a process.
That avoid the inconsistent results that grep of full ps output produces.
And it uses less resources that piping ps output through grep.

But checking for just synaptic is not really reliable since the dpkg lock can be held by other programs such as dpkg, apt-get, or aptitude.

[oodlesOfmoodles]

Thanks for your help and time.
The explanations of the commands really help.

Thanks again!