svn commit: r360786 - head/bin/ps

[Piotr Pawel Stefaniak]

Author: pstef
Date: Thu May  7 16:56:18 2020
New Revision: 360786
URL: https://svnweb.freebsd.org/changeset/base/360786

Log:
  ps: extend the non-standard option -d (tree view) to work with -p
  
  Initially it seemed that there were multiple possible ways to do it.
  
  Processing option -p could conditionally add selected processes and
  their descendants to the list for further work, but it is not guaranteed
  to know whether the -d option has been used or not, and it also doesn't
  have access to the process list just yet.
  
  There is also descendant_sort() which has access to all possibly needed
  information, but serves the purely post-processing purpose of sorting
  output.
  
  Then there is the loop that uses invocation information and full process
  list to create a list of processes for final display. It seems the most
  natural place to implement this, but indeterminate state of the process
  list and volatility of the final list that is being created obstruct
  adding an elegant search for all elements of process descendancy trees.
  
  So I opted for adding another loop, just before the one I mentioned
  above. For all selected processes it conditionally adds direct
  descendants to the end of this list of selected processes.
  
  Possible usage:
  * ps -auxd -p $$
  * ps -auxd -p 1
  * while x=$(pgrep svnlite); do clear; ps auxd -p $x; sleep 2; done
  * ps -auxd -p `pgrep make`
  
  Reviewed by:	kevans, kaktus (earlier version)
  MFC after:	1 week
  Differential Revision:	https://reviews.freebsd.org/D24380

Modified:
  head/bin/ps/ps.c

Modified: head/bin/ps/ps.c
==============================================================================
--- head/bin/ps/ps.c	Thu May  7 16:40:33 2020	(r360785)
+++ head/bin/ps/ps.c	Thu May  7 16:56:18 2020	(r360786)
@@ -506,7 +506,7 @@ main(int argc, char *argv[])
 			what = KERN_PROC_PGRP | showthreads;
 			flag = *pgrplist.l.pids;
 			nselectors = 0;
-		} else if (pidlist.count == 1) {
+		} else if (pidlist.count == 1 && !descendancy) {
 			what = KERN_PROC_PID | showthreads;
 			flag = *pidlist.l.pids;
 			nselectors = 0;
@@ -544,6 +544,14 @@ main(int argc, char *argv[])
 	if ((kp == NULL && errno != ESRCH) || (kp != NULL && nentries < 0))
 		xo_errx(1, "%s", kvm_geterr(kd));
 	nkept = 0;
+	if (descendancy)
+		for (elem = 0; elem < pidlist.count; elem++)
+			for (i = 0; i < nentries; i++)
+				if (kp[i].ki_ppid == pidlist.l.pids[elem]) {
+					if (pidlist.count >= pidlist.maxcount)
+						expand_list(&pidlist);
+					pidlist.l.pids[pidlist.count++] = kp[i].ki_pid;
+				}
 	if (nentries > 0) {
 		if ((kinfo = malloc(nentries * sizeof(*kinfo))) == NULL)
 			xo_errx(1, "malloc failed");