As it is with UNIX & Linux there is always another way. In my previous article [one-liner]: Filtering ps from ps, one reader, Christoph, mentioned an alternative method to the one I outlined. In this case, I would consider his to be a better way, so I thought I would take a second to demonstrate this alternative method. The alternative? Use the command pgrep.
The Original Approach
My original post offered the following one-liner:
1 2 3 4 5 6 7 8 9 10 | % ps -eaf | grep "[h]ttpd" root 2683 1 0 2008 ? 00:20:31 /usr/sbin/httpd apache 17146 2683 0 Aug30 ? 00:00:02 /usr/sbin/httpd apache 17147 2683 0 Aug30 ? 00:00:02 /usr/sbin/httpd apache 17149 2683 0 Aug30 ? 00:00:02 /usr/sbin/httpd apache 17150 2683 0 Aug30 ? 00:00:02 /usr/sbin/httpd apache 17151 2683 0 Aug30 ? 00:00:02 /usr/sbin/httpd apache 17152 2683 0 Aug30 ? 00:00:02 /usr/sbin/httpd apache 17153 2683 0 Aug30 ? 00:00:02 /usr/sbin/httpd apache 17154 2683 0 Aug30 ? 00:00:02 /usr/sbin/httpd |
This one-liner provided a list of all the httpd processes running, while filtering out the actual string from the grep httpd command.
The Alternative Approach
By using the command pgrep, the same effect can be achieved and a lot more. For starters, you can get a list of all the httpd PIDs:
1 2 3 4 5 6 7 8 9 | # list of httpd PIDs % pgrep httpd 1608 7645 9739 10051 27712 27859 |
This could be useful in a shell script, if needed, to check for any running httpd processes. For example:
1 2 3 4 | # test for httpd processes % [ -z "`pgrep httpd`" ] || echo "running" running |
Here are some other examples:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | # list of PIDs with corresponding command name % pgrep -l httpd 1608 httpd 7645 httpd 9739 httpd 10051 httpd 27712 httpd 27859 httpd # list of PIDs with corresponding command name owned by user root % pgrep -l -u root httpd 1608 httpd # list of PIDs, separated with a comma delimiter % pgrep -d, httpd 1608,7645,9739,14119,14162,27859 # detailed list of httpd PIDs via ps # NOTE: $(...) runs the command above, returning the list of PIDs to ps % ps -fp $(pgrep -d, httpd) UID PID PPID C STIME TTY TIME CMD root 1608 1 0 Aug03 ? 00:00:05 /usr/sbin/httpd apache 7645 1608 0 Sep04 ? 00:00:47 /usr/sbin/httpd apache 9739 1608 0 Sep04 ? 00:01:50 /usr/sbin/httpd apache 14119 1608 0 Sep04 ? 00:00:13 /usr/sbin/httpd apache 14162 1608 0 Sep04 ? 00:00:13 /usr/sbin/httpd apache 27859 1608 0 Sep04 ? 00:07:19 /usr/sbin/httpd |
Thanks again to Christoph for pointing out this alternative.
NOTE: For further details regarding my one-liner blog posts, check out my one-liner style guide primer.
September 5th, 2009, @ 1:13 am |
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