Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top
$ ps | grep django
28006 ttys004    0:01.12 /usr/bin/python bin/django celeryd --beat
51393 ttys005    0:01.45 /usr/bin/python bin/django celeryd -l INFO
51472 ttys005    0:01.29 /usr/bin/python bin/django celeryd -l INFO
51510 ttys005    0:01.89 /usr/bin/python bin/django celeryd -l INFO
51801 ttys005    0:01.83 /usr/bin/python bin/django celeryd -l INFO
53470 ttys005    0:03.97 /usr/bin/python bin/django celeryd -l INFO
53780 ttys005    0:00.00 grep django

Is there a way to prevent the last process (that is, the grep that was started at the same time as my ps command) being reported?

(I started trying to come up with a regex that would match the literal but not match itself, but that seemed, um, not the right approach...)

share|improve this question
up vote 4 down vote accepted

My answer is a variation on the typical answer for searching for "foobar" in a ps listing. The argument of "-A" "ps" is more portable than "aux", I believe, but this change is irrelevant to the answer. The typical answer looks like this:

$ ps -A -ww | grep [f]oobar

Instead I use this pattern:

$ ps -A -ww | grep [^]]foobar

The main advantage is that it's easier to write scripts based on this patterns because you simply concatenate a static string [^]] with whatever pattern you are looking for. You don't need to strip off the first letter of the string then insert it between the square braces and then concatenate the that back together again. When scripting in shell it's easier to simply stick [^]] in front of the pattern you were lookginfor looking for. String slicing in Bash is an ugly thing, so my variation avoids that. This variation says show the lines where the pattern matches WITHOUT a leading right-square-bracket ]. Since the search pattern to exclude a square bracket actually adds the square bracket to the pattern then it will never match itself.

So you could write a portable psgrep command as follows. Here, I make some allowance for differences between Linux, OS X BSD, and others. This adds the column headers from ps, provides a more custom ps format that suits my needs betters, and displays processes listing extra, extra wide so that none of the command-line arguments are missed. Well, most are not missed. Java being Java, it often does things in the worst possible way, so you some java services will run past the maximum allowed length of arguments that the process table will keep track of. I believe this is 1024 characters. The command-lone length allowed to start a process is much longer, but the kernel process table doesn't bother to keep track of anything over 1K in length. Once the command is started the command-name and argument list isn't needed against, so what gets stored in the process table is just informational.

psgrep ()
{
    pattern=[^]]${1};
    case "$(uname -s)" in
        Darwin)
            ps -A -ww -o pid,ppid,nice,pri,pcpu,pmem,etime,user,wchan,stat,command | grep -i -e "^[[:space:]]*PID" -e ${pattern}
        ;;
        Linux)
            ps -A -ww -o pid,ppid,tid,nice,pri,pcpu,pmem,etime,user,wchan:20,stat,command | grep -i -e "^[[:space:]]*PID" -e ${pattern}
        ;;
        *)  # other UNIX flavors get a minimalist version.
            ps -A -ww | grep -i -e ${pattern}
        ;;
    esac
}
share|improve this answer
    
Thanks, I really like this for the reasons given. – Steve Bennett Mar 6 at 22:17

+1 for @jamzed terse answer, however the OP might need some explanation:

ps | grep "[d]jango"

Using that regex you are launching a process which its ps string will not match itself, since the regexp matches "django" and not "[d]jango". That way you'll exclude the process that has the string "[d]jango" which in this case is grep; The same can be applied to pgrep, egrep, awk, sed, etc... whichever command you used to define the regex.

From man 7 regex

   A bracket expression is a list of characters enclosed in "[]".  It nor‐
   mally matches any single character from the list (but see  below).   If
   the  list  begins  with  '^',  it matches any single character (but see
   below) not from the rest of the list.  If two characters  in  the  list
   are  separated  by '-', this is shorthand for the full range of charac‐
   ters between those two (inclusive) in the collating sequence, for exam‐
   ple,  "[0-9]" in ASCII matches any decimal digit.  It is illegal(!) for
   two ranges to share an endpoint, for example, "a-c-e".  Ranges are very
   collating-sequence-dependent,  and portable programs should avoid rely‐
   ing on them.
share|improve this answer
2  
Cool. I'm actually pretty comfortable with regexs but couldn't immediately think of a way to prevent the regexp matching itself. Enclosing a letter in square brackets makes perfect sense. (Including something like [^!] would also work...) – Steve Bennett Mar 9 '12 at 11:23
1  
That's nice and crafty. – ash Mar 9 '12 at 21:09
    
For the 'ps' specific case, I use '[ ]' at the front of the process name I am searching for. Then I don't need to parse the process name specially for the regex, but it still matches. – Neromancer Nov 5 '14 at 11:05

ps | grep [d]jango

ps | grep d[j]ango

...

ps | grep djang[o]

share|improve this answer
    
Add space if you need to grep one char: ps aux| grep "[Z] " – A.D. Jun 5 '15 at 12:12

Use pgrep instead: pgrep -lf django

share|improve this answer
    
As usual I forgot to mention the platform (OS X in this case). Presumably pgrep works on various linuxes. – Steve Bennett Mar 9 '12 at 11:30
    
I don't agree, @ramruma . I came to this thread precisely because pgrepgives me exactly this problem. But I must say I am testing it in CygWin (where ps can not show the full command line of the process). – Sopalajo de Arrierez Apr 4 '14 at 2:28
    
The manual states "The running pgrep or pkill process will never report itself as a match.", and indeed I've not seen it do so. – deltab Mar 7 at 2:07

Oh wait, this works:

ps | grep django | grep -v grep
share|improve this answer
6  
Only if the process command line doesn't legitimately include grep, which you cannot count on in the general case. – Michael Kjörling Mar 9 '12 at 12:41

ps -d | grep django

from man ps:

 -d                  Lists information  about  all  processes
                     except session leaders.
share|improve this answer
    
still shows grep on mine... – Kevin Jun 23 '13 at 21:03
    
Yep, that works for me on OS X. – Steve Bennett Jan 29 '14 at 5:54
    
Doesn't work so well on Linux. – A-B-B Aug 18 '14 at 21:55
    
More generally, the options to ps are notoriously non-portable, so without information about which platform this is for, this answer isn't very helpful. Furthermore, this is obviously not adequate when you are not sure that the process you are looking for is not a process leader (i.e. this may help if your target is a daemon, but not generally otherwise). – tripleee Apr 5 at 11:51

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.