I am trying to check ( in a generic way ) that the shell that has just been started is not already running. I am getting bizarre counts of 3 or even 4 for the number of processes already running. I expect to see only 1 if it is just this instance or 2 if already running. In fact since adding the "grep -v ${thispid}" I expected to see 0 or 1 !!!

The sleep is so I can launch a test with "&" to background it then try to launch again. I think it has something to do with being in a sub-shell because of using pipes within "`" pre-execution quotes but I'm losing vast amounts of hair trying to figure out what I've done wrong. Any bright ideas ? Or any suggestions for a better/easier way of doing this ?

#!/bin/sh
#
# Test how to check whether already running
#
export thispid="$$"
echo "This PID = ${thispid}"
export thisshell="$0"
export thisproc="`basename ${thisshell}`"
echo "This proc = ${thisproc}"
export thisuser="`whoami`"
echo "This user = ${thisuser}"
txt="`ps -w -u ${thisuser} -O args | grep ${thisproc} | grep -v ${thispid} | grep -v grep`"
echo "${txt}"
counter="`ps -w -u ${thisuser} -O args | grep ${thisproc} | grep -v ${thispid} | grep -v grep | wc -l`"
echo "Count = ${counter}"
sleep 10m
exit

Here's some annotated example output from my shell.

bobs_test.sh
This PID = 31994
This proc = bobs_test.sh
This user = martini
31997 /bin/sh ./bobs_t R pts/8 00:00:00 /bin/sh ./bobs_test.sh
Count = 1
<<<<<<<<<<<< I CTL-Ced it here. Output as expected ( though why 1 instead of 0 ) >>>>>>>>>
[martini@dbvdev4108 Bin]$
[martini@dbvdev4108 Bin]$ !! &
bobs_test.sh &
[1] 32024
[martini@dbvdev4108 Bin]$ This PID = 32024
This proc = bobs_test.sh
This user = martini
32027 /bin/sh ./bobs_t R pts/8 00:00:00 /bin/sh ./bobs_test.sh
Count = 1

<<<<<<<<<<<< Backgrounded, again output as expected >>>>>>>>>

[martini@dbvdev4108 Bin]$ bobs_test.sh
This PID = 32039
This proc = bobs_test.sh
This user = martini
32024 /bin/sh ./bobs_t S pts/8 00:00:00 /bin/sh ./bobs_test.sh
32042 /bin/sh ./bobs_t R pts/8 00:00:00 /bin/sh ./bobs_test.sh
32045 [bobs_test.sh] R pts/8 00:00:00 [bobs_test.sh]
32046 /bin/sh ./bobs_t R pts/8 00:00:00 /bin/sh ./bobs_test.sh
Count = 3

<<<<<<<<<<<< WTF?!?! Previous still running + this one should = 2 >>>>>>>

[martini@dbvdev4108 Bin]$ <<<<<<<<< CTRL-C and try again >>>>>>>>>>>>
[martini@dbvdev4108 Bin]$ !!
bobs_test.sh
This PID = 32069
This proc = bobs_test.sh
This user = martini
32024 /bin/sh ./bobs_t S pts/8 00:00:00 /bin/sh ./bobs_test.sh
32072 /bin/sh ./bobs_t R pts/8 00:00:00 /bin/sh ./bobs_test.sh
Count = 2

<<<<<< Whaaaa ! Why 2 when it was 3 last run ? >>>>>>>>>>>

[martini@dbvdev4108 Bin]$ <<<<< CRTL-C a few more times and see if it happens again >>>>>>>>>>>
[martini@dbvdev4108 Bin]$ !!
bobs_test.sh
This PID = 32084
This proc = bobs_test.sh
This user = martini
32024 /bin/sh ./bobs_t S pts/8 00:00:00 /bin/sh ./bobs_test.sh
32087 /bin/sh ./bobs_t R pts/8 00:00:00 /bin/sh ./bobs_test.sh
Count = 2

[martini@dbvdev4108 Bin]$
[martini@dbvdev4108 Bin]$ !!
bobs_test.sh
This PID = 32099
This proc = bobs_test.sh
This user = martini
32024 /bin/sh ./bobs_t S pts/8 00:00:00 /bin/sh ./bobs_test.sh
32102 /bin/sh ./bobs_t R pts/8 00:00:00 /bin/sh ./bobs_test.sh
Count = 2

[martini@dbvdev4108 Bin]$
[martini@dbvdev4108 Bin]$ !!
bobs_test.sh
This PID = 32114
This proc = bobs_test.sh
This user = martini
32024 /bin/sh ./bobs_t S pts/8 00:00:00 /bin/sh ./bobs_test.sh
32117 /bin/sh ./bobs_t R pts/8 00:00:00 /bin/sh ./bobs_test.sh
32121 /bin/sh ./bobs_t R pts/8 00:00:00 /bin/sh ./bobs_test.sh
Count = 3

<<<<<<<<<<<<< No !!! Not again ? My Ox is flummed and my ghast is flabbered >>>>>>>>

N.B. I did check the obvious : Nobody else is logged in trying my test script .

Moin,

I think it's a problem of the variuos subshells (forks) you are creating be using "`...`" command substitution and pipes (/bin/sh is bash on your system?). The "-w" output format of ps does not show the PPID (parent process id), so you don't filter children out with "grep -v ${thispid}". Try the "-f" option instead.

You should check, if the pidof command is available on your system, it makes your work much easier ;-)



Jan

Danke !

pidof isn't available but grepping out child processes solved my problem.

( /bin/sh was an attempt to see if it still went wrong in another shell )