pidof: size optimizations (-50 bytes)

3 files changed, 44 insertions, 20 deletions

diff --git a/include/usage.h b/include/usage.h
index 2baa495ac..6d02c8bbf 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -2544,7 +2544,7 @@
         USE_FEATURE_PIDOF_SINGLE( \
        "\n      -s      Display only a single PID") \
         USE_FEATURE_PIDOF_OMIT( \
-       "\n      -o      Omit given pid") \
+       "\n      -o PID  Omit given pid") \
         USE_FEATURE_PIDOF_OMIT( \
        "\n              Use %PPID to omit the parent pid of pidof itself")
 #define pidof_example_usage \
diff --git a/libbb/find_pid_by_name.c b/libbb/find_pid_by_name.c
index e98616940..13ccb545d 100644
--- a/libbb/find_pid_by_name.c
+++ b/libbb/find_pid_by_name.c
@@ -9,6 +9,35 @@
 
 #include "libbb.h"
 
+/*
+In Linux we have three ways to determine "process name":
+1. /proc/PID/stat has "...(name)...", among other things. It's so-called "comm" field.
+2. /proc/PID/cmdline's first NUL-terminated string. It's argv[0] from exec syscall.
+3. /proc/PID/exe symlink. Points to the running executable file.
+
+kernel threads:
+ comm: thread name
+ cmdline: empty
+ exe: <readlink fails>
+
+executable
+ comm: first 15 chars of base name
+ (if executable is a symlink, then first 15 chars of symlink name are used)
+ cmdline: argv[0] from exec syscall
+ exe: points to executable (resolves symlink, unlike comm)
+
+script (an executable with #!/path/to/interpreter):
+ comm: first 15 chars of script's base name (symlinks are not resolved)
+ cmdline: /path/to/interpreter (symlinks are not resolved)
+ (script name is in argv[1], args are pushed into argv[2] etc)
+ exe: points to interpreter's executable (symlinks are resolved)
+
+If FEATURE_PREFER_APPLETS=y (and more so if FEATURE_SH_STANDALONE=y),
+some commands started from busybox shell, xargs or find are started by
+execXXX("/proc/self/exe", applet_name, params....)
+and therefore comm field contains "exe".
+*/
+
 /* find_pid_by_name()
  *
  *  Modified by Vladimir Oleynik for use with libbb/procps.c
diff --git a/procps/pidof.c b/procps/pidof.c
index 3541aeee0..01e587cbf 100644
--- a/procps/pidof.c
+++ b/procps/pidof.c
@@ -20,9 +20,9 @@ int pidof_main(int argc, char **argv);
 int pidof_main(int argc, char **argv)
 {
         unsigned first = 1;
-        unsigned fail = 1;
         unsigned opt;
 #if ENABLE_FEATURE_PIDOF_OMIT
+        char ppid_str[sizeof(int)*3 + 1];
         llist_t *omits = NULL; /* list of pids to omit */
         opt_complementary = "o::";
 #endif
@@ -35,14 +35,12 @@ int pidof_main(int argc, char **argv)
 #if ENABLE_FEATURE_PIDOF_OMIT
         /* fill omit list.  */
         {
-                char getppid_str[sizeof(int)*3 + 1];
-                llist_t * omits_p = omits;
+                llist_t *omits_p = omits;
                 while (omits_p) {
                         /* are we asked to exclude the parent's process ID?  */
-                        if (!strncmp(omits_p->data, "%PPID", 5)) {
-                                llist_pop(&omits_p);
-                                snprintf(getppid_str, sizeof(getppid_str), "%u", (unsigned)getppid());
-                                llist_add_to(&omits_p, getppid_str);
+                        if (strcmp(omits_p->data, "%PPID") == 0) {
+                                sprintf(ppid_str, "%u", (unsigned)getppid());
+                                omits_p->data = ppid_str;
                         }
                         omits_p = omits_p->link;
                 }
@@ -56,27 +54,24 @@ int pidof_main(int argc, char **argv)
                 /* reverse the pidlist like GNU pidof does.  */
                 pidList = pidlist_reverse(find_pid_by_name(argv[optind]));
                 for (pl = pidList; *pl; pl++) {
-                        SKIP_FEATURE_PIDOF_OMIT(const) unsigned omitted = 0;
 #if ENABLE_FEATURE_PIDOF_OMIT
                         if (opt & OPT_OMIT) {
                                 llist_t *omits_p = omits;
                                 while (omits_p) {
                                         if (xatoul(omits_p->data) == *pl) {
-                                                omitted = 1;
-                                                break;
-                                        } else
-                                                omits_p = omits_p->link;
+                                                goto omitting;
+                                        }
+                                        omits_p = omits_p->link;
                                 }
                         }
 #endif
-                        if (!omitted) {
-                                printf(" %u" + first, (unsigned)*pl);
-                                first = 0;
-                        }
-                        fail = (!ENABLE_FEATURE_PIDOF_OMIT && omitted);
-
+                        printf(" %u" + first, (unsigned)*pl);
+                        first = 0;
                         if (ENABLE_FEATURE_PIDOF_SINGLE && (opt & OPT_SINGLE))
                                 break;
+#if ENABLE_FEATURE_PIDOF_OMIT
+ omitting: ;
+#endif
                 }
                 free(pidList);
                 optind++;
@@ -87,5 +82,5 @@ int pidof_main(int argc, char **argv)
         if (ENABLE_FEATURE_CLEAN_UP)
                 llist_free(omits, NULL);
 #endif
-        return fail ? EXIT_FAILURE : EXIT_SUCCESS;
+        return first; /* 1 (failure) - no processes found */
 }