-n and -p suck up ARGV no matter what

mpersico has asked for the wisdom of the Perl Monks concerning the following question:

I have this line of code in a loop in shell:

 pid=$(ps -l -p $pid | grep -v PPID | perl -ane 'print $F[4]')
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The idea is to get the parent of the process. Other code is checking for other conditions. But that's not the problem. The problem is that $F[4] only works on some 'ps'. For the 'ps' in Cygwin, I need to use $F[1]. Sooooo, I naively tried this:

ppidi=4
[ $(uname) = 'Cygwin ] && ppidi=1

...

 pid=$(ps -l -p $pid | grep -v PPID | \
perl -ane 'print $F[$ARGV[0]]' $ppidi);
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which resulted in

Can't open 1: No such file or directory.
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In short, once you use -n or -p, there is no way to use ARGV as arguments, and not have them sucked up as filenames to feed to the virtual while(<>) {} loop, is there?

Comment on -n and -p suck up ARGV no matter what Select or Download Code

Replies are listed 'Best First'.
Re: -n and -p suck up ARGV no matter what by tybalt89 (Monsignor) on Oct 21, 2016 at 21:04 UTC
This is perl, be very careful of saying "no matter what". `echo -e "one\ntwo\nthree" \| perl -ne 'INIT{$tmp = shift} print "$tmp - +> $_"' 42` [download]	[reply] [d/l]
Re^2: -n and -p suck up ARGV no matter what by mpersico (Monk) on Oct 22, 2016 at 03:01 UTC
I knew someone would take that as a challenge. :-) Thank you.	[reply]
Re: -n and -p suck up ARGV no matter what by stevieb (Canon) on Oct 21, 2016 at 20:44 UTC
With Perl, you can simply use `getppid()`, but since this isn't perl, you can use this: `ps -o ppid= -p $pid` [download] ...and that should get you your parent PID without having to use Perl, sed etc.	[reply] [d/l] [select]
Re: -n and -p suck up ARGV no matter what by mpersico (Monk) on Oct 21, 2016 at 20:41 UTC
Oh my goodness, I am so stupid. I should just parse the header looking for which column is PPID and use that. `ps -l -p $$ \| grep PPID \| perl -ane '$i=0; while($i<@F && $F[$i] ne q(PPID)){$i++}; print $i if $i < @F'` [download]	[reply] [d/l]