Index: strace-4.12/strace.1

===================================================================

--- strace-4.12.orig/strace.1	2016-05-26 17:34:28.000000000 +0200

+++ strace-4.12/strace.1	2018-04-30 13:08:34.770163287 +0200

@@ -601,10 +601,13 @@

 is used.

 .LP

 When using

-.BR \-p ,

+.B \-p

+without a

+.IR command ,

 the exit status of

 .B strace

-is zero unless there was an unexpected error in doing the tracing.

+is zero unless no processes has been attached or there was an unexpected error

+in doing the tracing.

 .SH "SETUID INSTALLATION"

 If

 .B strace

Index: strace-4.12/strace.c

===================================================================

--- strace-4.12.orig/strace.c	2018-04-30 13:07:36.776730188 +0200

+++ strace-4.12/strace.c	2018-04-30 13:08:34.771163277 +0200

@@ -138,7 +138,7 @@

 /* Are we "strace PROG" and need to hide everything until execve? */

 bool hide_log_until_execve = 0;

-static int exit_code = 0;

+static int exit_code;

 static int strace_child = 0;

 static int strace_tracer_pid = 0;

@@ -2446,6 +2446,8 @@

 {

 	init(argc, argv);

+	exit_code = !nprocs;

+

 	while (trace())

 		;