only seeing successful system calls

[Marty Leisner]

When using strace I  sometimes like to see the system calls
which work (instead of all the system calls).

I've been porting this patch for years, it seems very useful.

With the -z option, you don't see opens on files which aren't there
(very useful tracking down what a program actually does, instead of
trying to do).


+++ strace.c	2002/11/03 05:23:31
@@ -67,6 +67,9 @@
 int iflag = 0, xflag = 0, qflag = 0;
 int pflag_seen = 0;
 
+/* set when only successful syscalls are printed */
+int only_zeros = 0;
+
 char *username = NULL;
 uid_t run_uid;
 gid_t run_gid;
@@ -154,6 +157,7 @@
 -s strsize -- limit length of print strings to STRSIZE chars (default %d)\n\
 -S sortby -- sort syscall counts by: time, calls, name, nothing (default %s)\n\
 -u username -- run command as username handling setuid and/or setgid\n\
+-z -- print sys calls returning 0 (normally succeeding)\n\
 ", DEFAULT_ACOLUMN, DEFAULT_STRLEN, DEFAULT_SORTBY);
 	exit(exitval);
 }
@@ -190,7 +194,7 @@
 	set_sortby(DEFAULT_SORTBY);
 	set_personality(DEFAULT_PERSONALITY);
 	while ((c = getopt(argc, argv,
-		"+cdfFhiqrtTvVxa:e:o:O:p:s:S:u:")) != EOF) {
+		"+cdfFhiqrtTvVxza:e:o:O:p:s:S:u:")) != EOF) {
 		switch (c) {
 		case 'c':
 			cflag++;
@@ -234,6 +238,9 @@
 			printf("%s\n", version);
 			exit(0);
 			break;
+		case 'z':
+			only_zeros = 1;
+			break;
 		case 'a':
 			acolumn = atoi(optarg);
 			break;
--- syscall.c	2002/10/07 14:31:11	1.38
+++ syscall.c	2002/11/03 05:23:31
@@ -1742,8 +1742,13 @@
 		if (tcp->scno >= nsyscalls || tcp->scno < 0
 		    || (qual_flags[tcp->scno] & QUAL_RAW))
 			sys_res = printargs(tcp);
-		else
+		else {
+			extern int only_zeros;
+
+			if(only_zeros && tcp->u_error)
+				return;	/* ignore non-working syscalls */
 			sys_res = (*sysent[tcp->scno].sys_func)(tcp);
+		}	
 		u_error = tcp->u_error;
 		tprintf(") ");
 		tabto(acolumn);


marty leisner