mirror of https://github.com/tLDP/LDP
86 lines
2.6 KiB
Bash
86 lines
2.6 KiB
Bash
#!/bin/bash
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# pid-identifier.sh:
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# Gives complete path name to process associated with pid.
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ARGNO=1 # Number of arguments the script expects.
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E_WRONGARGS=65
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E_BADPID=66
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E_NOSUCHPROCESS=67
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E_NOPERMISSION=68
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PROCFILE=exe
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if [ $# -ne $ARGNO ]
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then
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echo "Usage: `basename $0` PID-number" >&2 # Error message >stderr.
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exit $E_WRONGARGS
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fi
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pidno=$( ps ax | grep $1 | awk '{ print $1 }' | grep $1 )
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# Checks for pid in "ps" listing, field #1.
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# Then makes sure it is the actual process, not the process invoked by this script.
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# The last "grep $1" filters out this possibility.
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#
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# pidno=$( ps ax | awk '{ print $1 }' | grep $1 )
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# also works, as Teemu Huovila, points out.
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if [ -z "$pidno" ] # If, after all the filtering, the result is a zero-length string,
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then #+ no running process corresponds to the pid given.
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echo "No such process running."
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exit $E_NOSUCHPROCESS
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fi
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# Alternatively:
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# if ! ps $1 > /dev/null 2>&1
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# then # no running process corresponds to the pid given.
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# echo "No such process running."
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# exit $E_NOSUCHPROCESS
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# fi
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# To simplify the entire process, use "pidof".
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if [ ! -r "/proc/$1/$PROCFILE" ] # Check for read permission.
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then
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echo "Process $1 running, but..."
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echo "Can't get read permission on /proc/$1/$PROCFILE."
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exit $E_NOPERMISSION # Ordinary user can't access some files in /proc.
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fi
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# The last two tests may be replaced by:
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# if ! kill -0 $1 > /dev/null 2>&1 # '0' is not a signal, but
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# this will test whether it is possible
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# to send a signal to the process.
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# then echo "PID doesn't exist or you're not its owner" >&2
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# exit $E_BADPID
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# fi
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exe_file=$( ls -l /proc/$1 | grep "exe" | awk '{ print $11 }' )
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# Or exe_file=$( ls -l /proc/$1/exe | awk '{print $11}' )
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#
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# /proc/pid-number/exe is a symbolic link
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#+ to the complete path name of the invoking process.
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if [ -e "$exe_file" ] # If /proc/pid-number/exe exists,
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then #+ then the corresponding process exists.
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echo "Process #$1 invoked by $exe_file."
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else
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echo "No such process running."
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fi
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# This elaborate script can *almost* be replaced by
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# ps ax | grep $1 | awk '{ print $5 }'
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# However, this will not work...
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#+ because the fifth field of 'ps' is argv[0] of the process,
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#+ not the executable file path.
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#
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# However, either of the following would work.
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# find /proc/$1/exe -printf '%l\n'
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# lsof -aFn -p $1 -d txt | sed -ne 's/^n//p'
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# Additional commentary by Stephane Chazelas.
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exit 0
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