Avoid running unnecessary repetitive ps command Post: 303011083

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Top Forums Shell Programming and Scripting Avoid running unnecessary repetitive ps command Post 303011083 by Don Cragun on Friday 12th of January 2018 04:01:49 PM

01-12-2018

Registered User

Quote:

Originally Posted by MadeInGermany

post#4 is unprecise (like post#1), for example will find pid 22 when searching for 2.
While the overall sense is not clear for me, this is certainly *not* intended.
Fix:

Code:

ps -ef | awk -vGPID="$gpid" '($2 == GPID || $3 == GPID)'

Doesn't give this the same result as the code in post#3 ?
Smilie

No. It doesn't give the same result as the code in post #3. With slightly modified versions of these scripts:
./tester:

Code:

#!/bin/ksh
gpid=${1:-$$}
ps -ef | tee ps.out | awk -v gpid="$gpid" '
{	line[NR] = $0
	pid[NR] = $2
	ppid[NR] = $3
}
$2 == gpid || $3 == gpid {
	PrintPid[$2]
	PrintPid[$3]
}
END {	for(i = 1; i <= NR; i++)
		if(pid[i] in PrintPid || ppid[i] in PrintPid)
			print line[i]
}'

Note that this captures the output from ps in ps.out which will be used as input for the other two scripts instead of rerunning ps. The above script produces the output:

Code:

  501   766   763   0  7Dec17 ttys003    0:01.40 -ksh
  501 27188   766   0 12:40PM ttys003    0:01.01 du /
  501 27189   766   0 12:40PM ttys003    0:00.01 /bin/ksh ./tester
    0 27190 27189   0 12:40PM ttys003    0:00.00 ps -ef
  501 27191 27189   0 12:40PM ttys003    0:00.00 tee ps.out
  501 27192 27189   0 12:40PM ttys003    0:00.00 awk -v gpid 27189

during a period where the command du / > du.out was running in the background while this script was running.

With this version of SkySmart's code modified to read from the ps.out produced by the above script:
./SkySmart:

Code:

#!/bin/ksh
gpid=${1:-$$}
APIDS=$(echo $(awk -v gpid="${gpid}" '$2 == gpid || $3 == gpid {print $2,$3}' ps.out) | sed 's~ ~|~g')
AllProcs=$(awk -v allpids="${APIDS}" '$2 ~ allpids || $3 ~ allpids {print $0}' ps.out | sed '/^$/d')
printf '%s\n' "$AllProcs"

and run with the operand 27189, we get the output:

Code:

  501   766   763   0  7Dec17 ttys003    0:01.40 -ksh
  501 27188   766   0 12:40PM ttys003    0:01.01 du /
  501 27189   766   0 12:40PM ttys003    0:00.01 /bin/ksh ./tester
    0 27190 27189   0 12:40PM ttys003    0:00.00 ps -ef
  501 27191 27189   0 12:40PM ttys003    0:00.00 tee ps.out
  501 27192 27189   0 12:40PM ttys003    0:00.00 awk -v gpid 27189

which is identical to the output produced by the code in post #3. But with a similarly modified version of MadeInGermany's code:
./MadeInGermany:

Code:

#!/bin/ksh
gpid=${1:-$$}
awk -v GPID="$gpid" '($2 == GPID || $3 == GPID)' ps.out

and run with the operand 27189, we only get the output:

Code:

  501 27189   766   0 12:40PM ttys003    0:00.01 /bin/ksh ./tester
    0 27190 27189   0 12:40PM ttys003    0:00.00 ps -ef
  501 27191 27189   0 12:40PM ttys003    0:00.00 tee ps.out
  501 27192 27189   0 12:40PM ttys003    0:00.00 awk -v gpid 27189

MadeInGermany's simpler code doesn't catch the parent, sibling, or grandchild processes of the process specified by $gpid. It only catches the process specified by $gpid and its children.

I do, however, agree that SkySmart's code works by accident when $gpid specifies a PID that isn't small enough to accidentally match several other unintended PIDs of unrelated running processes.

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