What is a .pid file and what does it contain?

linux unix pid
ifixthat picture ifixthat · Nov 28, 2011 · Viewed 169.3k times · Source

I recently come across a file with the extension .pid and explored inside it but didn't find much. The documentation says:

A Pid-File is a file containing the process identification number (pid) that is stored in a well-defined location of the filesystem thus allowing other programs to find out the pid of a running script.

Can anyone shed more light on this, or guide me to details of what's contained in the pid file?

Answer

Rafael Steil picture Rafael Steil · Nov 28, 2011

The pid files contains the process id (a number) of a given program. For example, Apache HTTPD may write its main process number to a pid file - which is a regular text file, nothing more than that - and later use the information there contained to stop itself. You can also use that information to kill the process yourself, using cat filename.pid | xargs kill

Related questions

Getting PID of process in Shell Script

I am writing one shell script and I want to get PID of one process with name as "ABCD". What i did was : process_id=`/bin/ps -fu $USER|grep "ABCD"|awk '{print $2}'` This gets PID of two …

Read More
Must my pidfile be located in /var/run?

I'm asking in both contexts: technically and stylistically. Can my application/daemon keep a pidfile in /opt/my_app/run/? Is it very bad to do so? My need is this: my daemon runs under a specific user, and the …

Read More
killing Parent process along with child process using SIGKILL

I am writing one shell script in which I have parent process and it has child processes which are created by sleep & command. Now I wish to kill the parent process so that the child process will be also …

Read More