CODEWITHSUNDEEP
linuxbashshellcommand-lineps
shkschneider
shkschneider

Reputation: 18243

ps: Clean way to only get parent processes?

I use ps ef and ps rf a lot.

Here is a sample output for ps rf:

  PID TTY      STAT   TIME COMMAND
 3476 pts/0    S      0:00 su ...
 3477 pts/0    S      0:02  \_ bash
 8062 pts/0    T      1:16      \_ emacs -nw ...
15733 pts/0    R+     0:00      \_ ps xf
15237 ?        S      0:00 uwsgi ...
15293 ?        S      0:00  \_ uwsgi ...
15294 ?        S      0:00  \_ uwsgi ...

And today I needed to retrieve only the master process of uwsgi in a script (so I want only 15237 but not 15293 nor 15294).

As of today, I tried some ps rf | grep -v ' \\_ '... but I would like a cleaner way.

I also came accross another solution from unix.com's forums:

ps xf | sed '1d' | while read pid tty stat time command ; do [ -n "$(echo $command | egrep '^uwsgi')" ] && echo $pid ; done

But still a lot of pipes and ugly tricks.

Is there really no ps option or cleaner tricks (maybe using awk) to accomplish that?

Upvotes: 12

Views: 28674

Answers (8)

reardenlife
reardenlife

Reputation: 317

By filename (outputs the number of parents):

o=""; for p in $(pgrep -f example.sh); do o="${o}$(pstree -lp | grep -nF \($p\))\n"; done; echo -e "$o" | cut -f2 -d: | cut -f2 -d- | sort -n | grep -vE ^$ | uniq -c | awk '$1>0' | wc -l

Edit: I previously used 

| cut -f1 -d: |

But apparently there is no guarantee that child processes will follow one after another so I ended up with counting parent processes by their name and pid:

| cut -f2 -d: | cut -f2 -d- |

Upvotes: 0

Bodo
Bodo

Reputation: 91

/usr/bin/pgrep -o <process_name>

where '-o' is the oldest (least recently started) of the matching processes

Upvotes: 9

user2435913
user2435913

Reputation: 1

If you can safely assume that you only have one parent process with n children, or that you only care about the 'earliest' of several parent processes (lowest PID), then I think this simpler solution works just fine.

ps h -opid -C<commandname> | head -1

Upvotes: 0

Uğur Engin
Uğur Engin

Reputation: 9

It is an other solution to get master process ID of a process.Tall, but nice.

pstree -p 1 |grep <proc_name>|sed -n 1p|tr -d "|,-"|sed 's/(/ /g'|sed 's/)/ /g'|tr -d "+"|awk {'print $2'};

Upvotes: 0

carpenter
carpenter

Reputation: 33

From key words KEYWORD

ps aux | grep -i KEYWORD | grep -v grep | awk '{print $2}'|sort -h|head -1|xargs kill

BTW, is this assumption that parent process ID is the smallest ID valid？？？？

Upvotes: -1

Albert
Albert

Reputation: 68110

Another solution (from here):

ps -ocommand= -p $PPID | awk -F/ '{print $NF}' | awk '{print $1}'

Upvotes: 1

roberto
roberto

Reputation: 12933

Why do not you simply save the pid of the master in a file (pidfile) with the --pidfile option ? If it is not a viable solution you can give a custom name to the master process with --procname-master .

Using ps for that kind of things is highly unreliable (race conditions all over the place, and special cases invalidating parsing rules...)

Upvotes: 0

c00kiemon5ter
c00kiemon5ter

Reputation: 17594

After discussing with @netcoder on his answer's comments he used a nice trick :D
Using f on ps will always get the parent on top which is great.

This should just work:

$ ps hf -opid -C <process> | awk '{ print $1; exit }'

as I mention on the comments, this will return the pid of just one process.

I would go with:

ps rf -opid,cmd -C <process-name> | awk '$2 !~ /^[|\\]/ { print $1 }'

that is:

  • list running processses r (or e if you want everything)
  • along with parent/children graph f
  • output only the pid and command name -opid,cmd
  • only for the given process -C <process>

and then

  • if the 2nd field - which is the command (-opid,cmd) - does not start with a \ or | then it is a parent process, so print the 1st field - which is the pid.

simple test:

$ ps f -opid,cmd -Cchromium
  PID CMD
 2800 /usr/lib/chromium/chromium --type=zygote --enable-seccomp-sandbox
 2803  \_ /usr/lib/chromium/chromium --type=zygote --enable-seccomp-sandbox
 2899      \_ /usr/lib/chromium/chromium --type=renderer --enable-seccomp-sandbox --lang=en-US --force-fieldtrials=ConnCountImpact/conn_count_6/ConnnectB
 2906      |   \_ /usr/lib/chromium/chromium --type=renderer --enable-seccomp-sandbox --lang=en-US --force-fieldtrials=ConnCountImpact/conn_count_6/Connn
 [  ... snip ... ]
 2861      \_ /usr/lib/chromium/chromium --type=renderer --enable-seccomp-sandbox --lang=en-US --force-fieldtrials=ConnCountImpact/conn_count_6/ConnnectB
 2863          \_ /usr/lib/chromium/chromium --type=renderer --enable-seccomp-sandbox --lang=en-US --force-fieldtrials=ConnCountImpact/conn_count_6/Connn
 2794 /usr/lib/chromium/chromium --enable-seccomp-sandbox --memory-model=low --purge-memory-button --disk-cache-dir=/tmp/chromium
 2796  \_ /usr/lib/chromium/chromium --enable-seccomp-sandbox --memory-model=low --purge-memory-button --disk-cache-dir=/tmp/chromium
 3918  \_ /usr/lib/chromium/chromium --type=gpu-process --channel=2794.45.1891443837 --gpu-vendor-id=0x10de --gpu-device-id=0x0611 --gpu-driver-version -
25308  \_ [chromium] <defunct>
31932  \_ /usr/lib/chromium/chromium --type=plugin --plugin-path=/usr/lib/mozilla/plugins/libflashplayer.so --lang=en-US --channel=2794.1330.1990362572


$ ps f -opid,cmd -Cchromium | awk '$2 !~ /^[|\\]/ { print $1 }'
PID
2800
2794

$ # also supressing the header of ps (top line 'PID') -- add 'h' to ps
$ ps hf -opid,cmd -Cchromium | awk '$2 !~ /^[|\\]/ { print $1 }'
2800
2794

Upvotes: 16

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