.. -*- coding: utf-8 -*- .. role:: sref(numref) .. role:: xref(numref) .. Copyright (C) 2022, Wolfgang Scherer, .. This file is part of Development. .. Permission is granted to copy, distribute and/or modify this document .. under the terms of the GNU Free Documentation License, Version 1.3 .. or any later version published by the Free Software Foundation; .. with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. .. A copy of the license is included in the section entitled "GNU .. Free Documentation License". .. inline comments (with du_comment_role) .. role:: rem(comment) .. role:: html(raw) :format: html .. role:: shx(code) :language: sh .. rst-class:: narrow xmedium xlarge xhuge xultra ################################################## :rem:`|||:sec:|||`\ shell PIDs ################################################## .. >>CODD See `the components of a doctoral dissertation and their order `_ .. >>CODD Dedication .. >>CODD Epigraph .. >>CODD Abstract .. compound:: .. \|:here:| .. >>CODD Introduction .. >>CODD Chapter See also `linux - How to get PID from forked child process in shell script - Stack Overflow `_. The script, child and parent PIDs can always be determined correctly in the parent script independent of the method employed to start it:: child () { :; } child & ( child ) & sh -c "child () { :; }; child" & script_pid="${$}" # PID of the running shell script child_pid="${!}" # last started child process parent_pid="${PPID}" # PID of parent process Whether the information is accesible in the child process depends on how the child process has been started. With the function:: child () { sleep "$( expr "${2-1}" '*' 5 )" script_pid="${3-}" child_pid="${$}" parent_pid="${PPID}" message="CHILD ${1-}" test x"${script_pid}" != x"${child_pid}" || message="${message}"' UNFORTUNATELY WRONG!' report sleep 20 } and the asynchrounous calls:: child FUNC "${indx}" "${$}" & ( child SUB "${indx}" "${$}" ) & sh -c "${FUNCTIONS} child SH "${indx}" \"${$}\"" & the output shows, that only the function invoked with an explicit ``sh -c`` has access to the correct PID/PPID information:: # -------------------------------------------------- # :PRC: CHILD FUNC UNFORTUNATELY WRONG! # :DBG: script_pid : [20634] # :DBG: child_pid : [20634] # :DBG: parent_pid : [10857] F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND 0 1114 10857 10853 20 0 2756840 1942820 poll_s Ssl ? 95:15 emacs 0 1114 20634 10857 20 0 4636 1732 wait Ss+ pts/22 0:00 sh /tmp/check_child_and_parent_pids.sh # -------------------------------------------------- # :PRC: CHILD SUB UNFORTUNATELY WRONG! # :DBG: script_pid : [20634] # :DBG: child_pid : [20634] # :DBG: parent_pid : [10857] F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND 0 1114 10857 10853 20 0 2756840 1942820 poll_s Ssl ? 95:15 emacs 0 1114 20634 10857 20 0 4636 1732 wait Ss+ pts/22 0:00 sh /tmp/check_child_and_parent_pids.sh # -------------------------------------------------- # :PRC: CHILD SH # :DBG: script_pid : [20634] # :DBG: child_pid : [20658] # :DBG: parent_pid : [20634] F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND 0 1114 20634 10857 20 0 4636 1732 wait Ss+ pts/22 0:00 sh /tmp/check_child_and_parent_pids.sh 0 1114 20658 20634 20 0 4636 1720 wait S+ pts/22 0:00 sh -c show_processes () { test -z The complete test script is:: FUNCTIONS="$( cat <<'EOF' show_processes () { test -z "${1-}" || printf "%s\n" "${1}" _sep= pids_rx= for _pid in "${script_pid}" "${child_pid}" "${parent_pid}" do test -n "${_pid}" || continue pids_rx="${pids_rx}${_sep}${_pid}" _sep='\|' done ps axl | head -1 ps axl | grep '^[^ ]* *[^ ]* *\('"${pids_rx}"'\)' | cut -c -107 | sort -k 3 } report () { printf "%s\n" "" printf >&2 "# --------------------------------------------------\n" printf >&2 "# "":PRC: %s\n" "${message}" test -z "${script_pid}" || \ printf >&2 "# "":DBG: %-${dbg_fwid-15}s: [%s]\n" "script_pid" "${script_pid}" test -z "${child_pid}" || \ printf >&2 "# "":DBG: %-${dbg_fwid-15}s: [%s]\n" "child_pid" "${child_pid}" test -z "${parent_pid}" || \ printf >&2 "# "":DBG: %-${dbg_fwid-15}s: [%s]\n" "parent_pid" "${parent_pid}" show_processes } child () { sleep "$( expr "${2-1}" '*' 5 )" script_pid="${3-}" child_pid="${$}" parent_pid="${PPID}" message="CHILD ${1-}" test x"${script_pid}" != x"${child_pid}" || message="${message}"' UNFORTUNATELY WRONG!' report sleep 20 } EOF )" eval "${FUNCTIONS}" shell_report () { script_pid="${$}" child_pid="${!}" parent_pid="${PPID}" sleep 1 message="SHELL ${indx}" report indx="$( expr "${indx}" + 1 )" } indx=1 child FUNC "${indx}" "${$}" & shell_report ( child SUB "${indx}" "${$}" ) & shell_report sh -c "${FUNCTIONS} child SH "${indx}" \"${$}\"" & shell_report sleep "$( expr "${indx}" '*' 5 )" The complete output is:: # -------------------------------------------------- # :PRC: SHELL 1 # :DBG: script_pid : [20634] # :DBG: child_pid : [20636] # :DBG: parent_pid : [10857] F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND 0 1114 10857 10853 20 0 2756840 1942820 poll_s Ssl ? 95:15 emacs 0 1114 20634 10857 20 0 4636 1728 wait Ss+ pts/22 0:00 sh /tmp/check_child_and_parent_pids.sh 1 1114 20636 20634 20 0 4636 104 wait S+ pts/22 0:00 sh /tmp/check_child_and_parent_pids.sh # -------------------------------------------------- # :PRC: SHELL 2 # :DBG: script_pid : [20634] # :DBG: child_pid : [20647] # :DBG: parent_pid : [10857] F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND 0 1114 10857 10853 20 0 2756840 1942820 - Rsl ? 95:15 emacs 0 1114 20634 10857 20 0 4636 1732 wait Ss+ pts/22 0:00 sh /tmp/check_child_and_parent_pids.sh 1 1114 20647 20634 20 0 4636 108 wait S+ pts/22 0:00 sh /tmp/check_child_and_parent_pids.sh # -------------------------------------------------- # :PRC: SHELL 3 # :DBG: script_pid : [20634] # :DBG: child_pid : [20658] # :DBG: parent_pid : [10857] F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND 0 1114 10857 10853 20 0 2756840 1942820 poll_s Ssl ? 95:15 emacs 0 1114 20634 10857 20 0 4636 1732 wait Ss+ pts/22 0:00 sh /tmp/check_child_and_parent_pids.sh 0 1114 20658 20634 20 0 4636 928 wait S+ pts/22 0:00 sh -c show_processes () { test -z # -------------------------------------------------- # :PRC: CHILD FUNC UNFORTUNATELY WRONG! # :DBG: script_pid : [20634] # :DBG: child_pid : [20634] # :DBG: parent_pid : [10857] F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND 0 1114 10857 10853 20 0 2756840 1942820 poll_s Ssl ? 95:15 emacs 0 1114 20634 10857 20 0 4636 1732 wait Ss+ pts/22 0:00 sh /tmp/check_child_and_parent_pids.sh # -------------------------------------------------- # :PRC: CHILD SUB UNFORTUNATELY WRONG! # :DBG: script_pid : [20634] # :DBG: child_pid : [20634] # :DBG: parent_pid : [10857] F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND 0 1114 10857 10853 20 0 2756840 1942820 poll_s Ssl ? 95:15 emacs 0 1114 20634 10857 20 0 4636 1732 wait Ss+ pts/22 0:00 sh /tmp/check_child_and_parent_pids.sh # -------------------------------------------------- # :PRC: CHILD SH # :DBG: script_pid : [20634] # :DBG: child_pid : [20658] # :DBG: parent_pid : [20634] F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND 0 1114 20634 10857 20 0 4636 1732 wait Ss+ pts/22 0:00 sh /tmp/check_child_and_parent_pids.sh 0 1114 20658 20634 20 0 4636 1720 wait S+ pts/22 0:00 sh -c show_processes () { test -z .. >>CODD Conclusion .. >>CODD Appendix A .. \|:here:| .. >>CODD Notes .. ================================================== .. :rem:`|||:sec:|||`\ Footnotes .. ================================================== :html:`
` .. \[#] .. \|:info:| put local references here .. \|:info:| put local definitions here .. include:: doc_defs.inc .. include:: abbrev_defs.inc .. include:: doc_defs_combined.inc .. .. \||<-snap->|| doc_standalone .. include:: doc/doc_defs_secret.inc .. \||<-snap->|| doc_standalone .. \||<-snap->|| not_doc_standalone .. include:: doc_defs_secret.inc .. \||<-snap->|| not_doc_standalone .. _`Wolfgang Scherer`: wolfgang.scherer@gmx.de