ps: add a new option -D to reimplement tree traversal

It takes a non-optional parameter string, one of "up", "down", or "both"
that can request tree traversal in the chosen directions. This adds PIDs
from the paths to the selection of PIDs and can be used together with -d
to draw a subset of the process tree.

Differential Revision:	https://reviews.freebsd.org/D41231

2 files changed, 61 insertions, 4 deletions

diff --git a/bin/ps/ps.1 b/bin/ps/ps.1
index 5fdecc4a3d4c..23868d8b3009 100644
--- a/bin/ps/ps.1
+++ b/bin/ps/ps.1
@@ -28,7 +28,7 @@
 .\"
 .\"     @(#)ps.1	8.3 (Berkeley) 4/18/94
 .\"
-.Dd April 25, 2023
+.Dd August 24, 2023
 .Dt PS 1
 .Os
 .Sh NAME
@@ -39,6 +39,7 @@
 .Op Fl -libxo
 .Op Fl aCcdefHhjlmrSTuvwXxZ
 .Op Fl O Ar fmt | Fl o Ar fmt
+.Op Fl D Ar up | down | both
 .Op Fl G Ar gid Ns Op , Ns Ar gid Ns Ar ...
 .Op Fl J Ar jid Ns Op , Ns Ar jid Ns Ar ...
 .Op Fl M Ar core
@@ -146,6 +147,18 @@ relative to each other.
 Note that this option has no effect if the
 .Dq command
 column is not the last column displayed.
+.It Fl D
+Expand the list of selected processes based on the process tree.
+.Dq UP
+will add the ancestor processes,
+.Dq DOWN
+will add the descendant processes, and
+.Dq BOTH
+will add both the ancestor and the descendant processes.
+.Fl D
+does not imply
+.Fl d ,
+but works well with it.
 .It Fl e
 Display the environment as well.
 .It Fl f
diff --git a/bin/ps/ps.c b/bin/ps/ps.c
index 8554a2eaa0a2..3a7a0f54cca0 100644
--- a/bin/ps/ps.c
+++ b/bin/ps/ps.c
@@ -168,7 +168,7 @@ static char vfmt[] = "pid,state,time,sl,re,pagein,vsz,rss,lim,tsiz,"
 			"%cpu,%mem,command";
 static char Zfmt[] = "label";
 
-#define	PS_ARGS	"AaCcde" OPT_LAZY_f "G:gHhjJ:LlM:mN:O:o:p:rSTt:U:uvwXxZ"
+#define	PS_ARGS	"AaCcD:de" OPT_LAZY_f "G:gHhjJ:LlM:mN:O:o:p:rSTt:U:uvwXxZ"
 
 int
 main(int argc, char *argv[])
@@ -188,6 +188,8 @@ main(int argc, char *argv[])
 	int fwidthmin, fwidthmax;
 	char errbuf[_POSIX2_LINE_MAX];
 	char fmtbuf[_POSIX2_LINE_MAX];
+	enum { NONE = 0, UP = 1, DOWN = 2, BOTH = 1 | 2 } directions = NONE;
+	struct { int traversed; int initial; } pid_count;
 
 	(void) setlocale(LC_ALL, "");
 	time(&now);			/* Used by routines in print.c. */
@@ -262,6 +264,20 @@ main(int argc, char *argv[])
 		case 'c':
 			cflag = 1;
 			break;
+		case 'D': {
+				size_t len = strlen(optarg);
+
+				if (len <= 2 &&
+					strncasecmp(optarg, "up", len) == 0)
+					directions |= UP;
+				else if (len <= 4 &&
+					strncasecmp(optarg, "down", len) == 0)
+					directions |= DOWN;
+				else if (len <= 4 &&
+					strncasecmp(optarg, "both", len) == 0)
+					directions |= BOTH;
+				break;
+			}
 		case 'd':
 			descendancy = 1;
 			break;
@@ -502,7 +518,7 @@ 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 && directions == NONE) {
 			what = KERN_PROC_PID | showthreads;
 			flag = *pidlist.l.pids;
 			nselectors = 0;
@@ -537,6 +553,33 @@ main(int argc, char *argv[])
 	if ((kp == NULL && errno != ESRCH) || (kp != NULL && nentries < 0))
 		xo_errx(1, "%s", kvm_geterr(kd));
 	nkept = 0;
+	pid_count.initial = pidlist.count;
+	if (directions & DOWN)
+		for (elem = 0; elem < pidlist.count; elem++)
+			for (i = 0; i < nentries; i++) {
+				if (kp[i].ki_ppid == kp[i].ki_pid)
+					continue;
+				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;
+				}
+			}
+	pid_count.traversed = pidlist.count;
+	if (directions & UP)
+		for (elem = 0; elem < pidlist.count; elem++) {
+			if (elem >= pid_count.initial && elem < pid_count.traversed)
+				continue;
+			for (i = 0; i < nentries; i++) {
+				if (kp[i].ki_ppid == kp[i].ki_pid)
+					continue;
+				if (kp[i].ki_pid == pidlist.l.pids[elem]) {
+					if (pidlist.count >= pidlist.maxcount)
+						expand_list(&pidlist);
+					pidlist.l.pids[pidlist.count++] = kp[i].ki_ppid;
+				}
+			}
+		}
 	if (nentries > 0) {
 		if ((kinfo = malloc(nentries * sizeof(*kinfo))) == NULL)
 			xo_errx(1, "malloc failed");
@@ -1448,10 +1491,11 @@ usage(void)
 {
 #define	SINGLE_OPTS	"[-aCcde" OPT_LAZY_f "HhjlmrSTuvwXxZ]"
 
-	(void)xo_error("%s\n%s\n%s\n%s\n",
+	(void)xo_error("%s\n%s\n%s\n%s\n%s\n",
 	    "usage: ps [--libxo] " SINGLE_OPTS " [-O fmt | -o fmt]",
 	    "          [-G gid[,gid...]] [-J jid[,jid...]] [-M core] [-N system]",
 	    "          [-p pid[,pid...]] [-t tty[,tty...]] [-U user[,user...]]",
+	    "          [-D up | down | both]",
 	    "       ps [--libxo] -L");
 	exit(1);
 }