Output messages to stderr

This allows capturing data from stdout of the traced command without
having trace-cmd messages mixed in.  "trace-cmd report" output still
goes to stdout.

In the process, I simplified the error-handling for splice, taking
advantage of die() automatically checking for errno and calling perror.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 5 insertions, 11 deletions

diff --git a/trace-cmd.c b/trace-cmd.c
index 6973bba..27fd2c9 100644
--- a/trace-cmd.c
+++ b/trace-cmd.c
@@ -361,7 +361,7 @@ static void enable_event(const char *name)
         char *path;
         int ret;
 
-        printf("enable %s\n", name);
+        fprintf(stderr, "enable %s\n", name);
         if (strcmp(name, "all") == 0) {
                 path = get_tracing_file("events/enable");
                 fp = fopen(path, "w");
@@ -550,17 +550,11 @@ static int create_recorder(int cpu)
 
         do {
                 ret = splice(in_fd, NULL, brass[1], NULL, page_size, 1 /* SPLICE_F_MOVE */);
-                if (ret < 0) {
-                        perror("in");
-                        printf("errno=%d\n", errno);
+                if (ret < 0)
                         die("splice in");
-                }
                 ret = splice(brass[0], NULL, out_fd, NULL, page_size, 3 /* and NON_BLOCK */);
-                if (ret < 0 && errno != EAGAIN) {
-                        perror("in");
-                        printf("errno=%d\n", errno);
+                if (ret < 0 && errno != EAGAIN)
                         die("splice out");
-                }
         } while (!finished);
 
         /* splice only reads full pages */
@@ -998,7 +992,7 @@ static void read_thread_data(void)
         }
 
         for (i = 0; i < cpu_count; i++) {
-                printf("offset=%llx\n", offsets[i]);
+                fprintf(stderr, "offset=%llx\n", offsets[i]);
                 ret = lseek64(output_fd, offsets[i], SEEK_SET);
                 if (ret < 0)
                         die("could not seek to %lld\n", offsets[i]);
@@ -1074,7 +1068,7 @@ int main (int argc, char **argv)
                                 if (plugin)
                                         die("only one plugin allowed");
                                 plugin = optarg;
-                                printf("  plugin %s\n", plugin);
+                                fprintf(stderr, "  plugin %s\n", plugin);
                                 break;
                         case 'd':
                                 disable = 1;