Index: bin/ps/ps.1
===================================================================
--- bin/ps/ps.1
+++ bin/ps/ps.1
@@ -224,6 +224,9 @@
 option.
 So the header texts for multiple keywords can be changed.
 If all keywords have empty header texts, no header line is written.
+.It Fl P
+Display information about processes whose parent matches the specified
+process IDs.
 .It Fl p
 Display information about processes which match the specified process IDs.
 .It Fl r
Index: bin/ps/ps.c
===================================================================
--- bin/ps/ps.c
+++ bin/ps/ps.c
@@ -170,12 +170,12 @@
 			"%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	"AaCcde" OPT_LAZY_f "G:gHhjJ:LlM:mN:O:o:p:P:rSTt:U:uvwXxZ"
 
 int
 main(int argc, char *argv[])
 {
-	struct listinfo gidlist, jidlist, pgrplist, pidlist;
+	struct listinfo gidlist, jidlist, pgrplist, pidlist, ppidlist;
 	struct listinfo ruidlist, sesslist, ttylist, uidlist;
 	struct kinfo_proc *kp;
 	KINFO *kinfo = NULL, *next_KINFO;
@@ -234,6 +234,7 @@
 	init_list(&jidlist, addelem_jid, sizeof(int), "jail id");
 	init_list(&pgrplist, addelem_pid, sizeof(pid_t), "process group");
 	init_list(&pidlist, addelem_pid, sizeof(pid_t), "process id");
+	init_list(&ppidlist, addelem_pid, sizeof(pid_t), "parent process id");
 	init_list(&ruidlist, addelem_uid, sizeof(uid_t), "ruser");
 	init_list(&sesslist, addelem_pid, sizeof(pid_t), "session id");
 	init_list(&ttylist, addelem_tty, sizeof(dev_t), "tty");
@@ -352,6 +353,13 @@
 			 */
 			nselectors++;
 			break;
+		case 'P':
+			/*
+			 * Non-standard option corresponding to Linux --ppid.
+			 */
+			add_list(&ppidlist, optarg);
+			nselectors++;
+			break;
 #if 0
 		case 'R':
 			/*-
@@ -558,6 +566,11 @@
 					if (kp->ki_pid == pidlist.l.pids[elem])
 						goto keepit;
 			}
+			if (ppidlist.count > 0) {
+				for (elem = 0; elem < ppidlist.count; elem++)
+					if (kp->ki_ppid == ppidlist.l.pids[elem])
+						goto keepit;
+			}
 			/*
 			 * Note that we had to process pidlist before
 			 * filtering out processes which do not have