pgrep cannot match some long filenames

[Mike Donovan]

Binary package hint: procps

pgrep has a bug in trying to match:
- a script with a long filename
- and its filename ends in a number

Example:

name this "myscriptwithalongfilename2"
#!/bin/sh
sleep 100000

chmod u+x myscriptwithalongfilename2
./myscriptwithalongfilename2 &

pgrep myscriptwithalongfilename2
[shows nothing]

ps -eF | grep myscriptwithalongfilename2
[will find the script]

This bug appears in Ubuntu Feisty Fawn.

[Tom Mortimer-Jones (tom-morty)]

I can replicate this.

It seems to be only seeing the first 15 characters of the script name.

pgrep myscriptwithalo
[shows PID]

pgrep myscriptwithalon
[shows nothing]

Is it using the output from ps -e? This seems to truncate the commands after 15 characters.

[Mike Donovan (mikedonovan80)]

You too noticed ps -e truncates process names.

At first, I suspected pgrep was a script over "ps -e"
but pgrep is a C executable.

ps and pgrep are both linked to libproc.so:
objdump -x /bin/ps | grep libproc
objdump -x /usr/bin/pgrep | grep libproc
NEEDED libproc-3.2.7.so

Probably/maybe a common function in libproc
has a bug/limitation.

--
Mike

--- Tom Mortimer-Jones <email address hidden> wrote:

> I can replicate this.
>
> It seems to be only seeing the first 15 characters
> of the script name.
>
> pgrep myscriptwithalo
> [shows PID]
>
> pgrep myscriptwithalon
> [shows nothing]
>
> Is it using the output from ps -e? This seems to
> truncate the commands
> after 15 characters.
>
> --
> pgrep cannot match some long filenames
> https://bugs.launchpad.net/bugs/113096
> You received this bug notification because you are a
> direct subscriber
> of the bug.
>

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[Mike Donovan (mikedonovan80)]

You too noticed ps -e truncates process names.

At first, I suspected pgrep was a script over "ps -e"
but pgrep is a C executable.

ps and pgrep are both linked to libproc.so:
objdump -x /bin/ps | grep libproc
objdump -x /usr/bin/pgrep | grep libproc
NEEDED libproc-3.2.7.so

Probably/maybe a common function in libproc
has a bug/limitation (?).

--
Mike

[Tom Mortimer-Jones (tom-morty)]

Looking at the man page for pgrep this isn't a bug. Looks like it is the default behaviour for backwards compatibility with the original Solaris version.

NOTES
       The process name used for matching is limited to the 15 characters present in the output of
       /proc/pid/stat. Use the -f option to match against the complete command line, /proc/pid/cmdline.

STANDARDS
       pkill and pgrep were introduced in Sun’s Solaris 7. This implementation is fully compatible.