Get PID of child threads

TS90 has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Get PID of child threads by oiskuu (Hermit) on Apr 03, 2017 at 22:15 UTC
Both `top` and `htop` will toggle the display of PID/TID when you press 'H'. The header, somewhat confusingly, remains "PID". In reality, the PID is shared between threads. The `ps` utility has a separate field for thread ID, called "LWP". In any case, this ID is accessible for the thread via gettid, a Linux-specific syscall... Here's a snippet that appears to work on my system: `use threads; sub gettid { use Config; die if $Config{archname} !~ /x86_64-linux/; syscall 186 } sub diag { print "pid=$$ tid=@{[threads->tid]} gettid=@{[gettid]}\n"; } async { diag }->join for 1..5;` [download] Edit. s/detach/join/, just in case.	[reply] [d/l]
Re^2: Get PID of child threads by TS90 (Novice) on Apr 03, 2017 at 22:29 UTC
Thanks, that works! The syscall for my OS (arm-linux-gnueabihf-thread-multi-64int) is 224. The following works. `use threads; sub gettid { syscall 224 } sub diag { print "pid=$$ tid=@{[threads->tid]} gettid=@{[gettid]}\n"; } async { diag }->detach for 1..5;` [download] pid=16490 tid=1 gettid=16493 pid=16490 tid=2 gettid=16494 pid=16490 tid=3 gettid=16495 pid=16490 tid=4 gettid=16496	[reply] [d/l]
Re: Get PID of child threads by Anonymous Monk on Apr 03, 2017 at 21:24 UTC
Threads are not processes, so they don't have PIDs.	[reply]
Re^2: Get PID of child threads by TS90 (Novice) on Apr 03, 2017 at 22:14 UTC
This is the output from `top` and `htop`. Each thread has it's own PID according to those: $ top -Hbn1 \| grep Control 16330 root 20 0 200444 74912 5776 S 5.5 7.9 0:06.74 Control.pl 16316 root 20 0 200444 74912 5776 S 0.0 7.9 0:02.23 Control.pl 16322 root 20 0 200444 74912 5776 S 0.0 7.9 0:00.00 Control.pl 16323 root 20 0 200444 74912 5776 S 0.0 7.9 0:00.69 Control.pl 16324 root 20 0 200444 74912 5776 S 0.0 7.9 0:01.61 Control.pl 16325 root 20 0 200444 74912 5776 S 0.0 7.9 0:00.70 Control.pl 16326 root 20 0 200444 74912 5776 S 0.0 7.9 0:01.60 Control.pl 16327 root 20 0 200444 74912 5776 S 0.0 7.9 0:00.00 Control.pl 16329 root 20 0 200444 74912 5776 S 0.0 7.9 0:00.08 Control.pl $ htop 16312 root 20 0 6184 3024 2716 S 0.0 0.3 0:00.02 │ │ └─ sudo ./Control.pl 16316 root 20 0 195M 74912 5776 S 3.3 7.9 0:09.58 │ │ └─ /usr/bin/perl ./Control.pl 16330 root 20 0 195M 74912 5776 S 2.3 7.9 0:04.29 │ │ ├─ /usr/bin/perl ./Control.pl 16329 root 20 0 195M 74912 5776 S 0.0 7.9 0:00.05 │ │ ├─ /usr/bin/perl ./Control.pl 16327 root 20 0 195M 74912 5776 S 0.0 7.9 0:00.00 │ │ ├─ /usr/bin/perl ./Control.pl 16326 root 20 0 195M 74912 5776 S 0.5 7.9 0:01.03 │ │ ├─ /usr/bin/perl ./Control.pl 16325 root 20 0 195M 74912 5776 S 0.0 7.9 0:00.45 │ │ ├─ /usr/bin/perl ./Control.pl 16324 root 20 0 195M 74912 5776 S 0.5 7.9 0:01.04 │ │ ├─ /usr/bin/perl ./Control.pl 16323 root 20 0 195M 74912 5776 S 0.0 7.9 0:00.44 │ │ ├─ /usr/bin/perl ./Control.pl 16322 root 20 0 195M 74912 5776 S 0.0 7.9 0:00.00 │ │ └─ /usr/bin/perl ./Control.pl	[reply] [d/l] [select]
Re^3: Get PID of child threads by Anonymous Monk on Apr 04, 2017 at 18:34 UTC
"Each thread has it's own PID according to those" Incorrect. Each thread has it's own ID given by something else.	[reply]
Re^2: Get PID of child threads by Anonymous Monk on Apr 03, 2017 at 21:32 UTC
It depends on the operating system	[reply]
Re^3: Get PID of child threads by stevieb (Canon) on Apr 03, 2017 at 21:37 UTC
As a curious observer on this thread, could you (or someone) provide examples on when a thread would have a pid, and when it wouldn't?	[reply]
Re: Get PID of child threads by beech (Parson) on Apr 03, 2017 at 21:23 UTC
Hi Try using POSIX::getpid()	[reply]
Re^2: Get PID of child threads by TS90 (Novice) on Apr 03, 2017 at 22:08 UTC
That gives the same results as using $$.	[reply]
Re^3: Get PID of child threads by beech (Parson) on Apr 03, 2017 at 22:54 UTC
Hi, In that case try getpid from Linux::Pid	[reply]