How Was My Script Run?

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

Replies are listed 'Best First'.
Re: How Was My Script Run? by JavaFan (Canon) on Mar 15, 2011 at 07:22 UTC
Assuming you aren't mucking around with pseudo terminals when calling your slave programs, you could just check whether STDIN is a terminal: `if (-t STDIN) { # Ran from the command line }` [download] This is a fairly standard way to check whether a program is run interactively (from the command-line) or not. An alternative way is to inspect the parent process. `getppid` returns the process ID of the parent, and from there you can work your way up. But I'd go the "check whether STDIN is a terminal" way.	[reply] [d/l] [select]
Re: How Was My Script Run? by cdarke (Prior) on Mar 15, 2011 at 09:21 UTC
In principle, get your parent process id. (getppid) then interrogate that. On UNIX you can use Proc::ProcessTable or walk the /proc directory tree. Example for Linux: `use warnings; use strict; my $ppid = getppid(); open (my $cmdfh, '<', "/proc/$ppid/cmdline") or die "Unable to open pp +id cmdline: $!"; my $cmdline = <$cmdfh>; close $cmdfh; if ($cmdline =~ /bash\|ksh\|csh/) { print "Started by a shell\n"; } elsif ($cmdline =~ /perl/) { print "Perl is the daddy\n"; } else { print "I was created by: $cmdline\n"; }` [download] On Windows it is not so easy. For some reason getppid is not implemented although there are Win32 API calls which will give details of the parent process based around `CreateToolhelp32Snapshot()` API.	[reply] [d/l] [select]
Re^2: How Was My Script Run? by Anonymous Monk on Mar 15, 2011 at 10:56 UTC
You can always do like `$ENV{I_AM_THE_PARENT_PROCESS_ALL_MY_KIDS} = "LOVE ME"; fork ...` [download] Even cpan/cpanplus does this	[reply] [d/l]
Re^3: How Was My Script Run? by HalNineThousand (Beadle) on Mar 15, 2011 at 16:11 UTC
When I try using: `if (-t STDIN) { $stdflag = 1; }` [download] I get the same result, whether I run my program from bash or if it's a spinoff from my Perl program, launched by system() or within backticks. I have no idea why, but that simply is not working on my system. When I use getppid() and get the command line from the /proc file system it works every time. What's important to me is that I have something that works so I don't have to set flags or be sure a parameter is passed on the command line. I can't use fork() to start the new process unless I make some significant changes in combining modules or USEing mods I don't want to on small daemon programs. But, as a point of interest, does anyone know why "-t STDIN" would still return a true when run from system() or with backticks? Thank you, everyone, for all the help!	[reply] [d/l]
Re^4: How Was My Script Run? by Anonymous Monk on Mar 15, 2011 at 16:18 UTC
Re^2: How Was My Script Run? by TomDLux (Vicar) on Mar 15, 2011 at 19:06 UTC
Slightly more general is to use the `ps` command. Unfortunately details vary on different varieties of Unix: 68$ cat /tmp/p.pl; perl /tmp/p.pl my $ppid= getppid(); my $job = `ps -o "cmd" -p $ppid`; print $job # ----- CMD /bin/ksh [download] As Occam said: Entia non sunt multiplicanda praeter necessitatem.	[reply] [d/l] [select]
Re: How Was My Script Run? by Anonymous Monk on Mar 15, 2011 at 06:52 UTC
Sure `set FROMCOMMANDLINE=myslave.pl perl myslave.pl --fromcommandline` [download] `export FROMCOMMANDLINE=myslave.pl perl myslave.pl --fromcommandline` [download]	[reply] [d/l] [select]
Re^2: How Was My Script Run? by HalNineThousand (Beadle) on Mar 15, 2011 at 06:59 UTC
So I'd have to do it by using a parameter as a flag? Is that the only way, or is there any way for a script to tell, such as by looking at input or output or something else that I wouldn't specify in a parameter?	[reply]
Re^3: How Was My Script Run? by Anonymous Monk on Mar 15, 2011 at 07:44 UTC
So I'd have to do it by using a parameter as a flag? Is that the only way, or is there any way for a script to tell, such as by looking at input or output or something else that I wouldn't specify in a parameter? Parameters are delicious, learn to love them :)	[reply]
Re^4: How Was My Script Run? by HalNineThousand (Beadle) on Mar 15, 2011 at 16:17 UTC