which: -a support (needed for bfin uclibc build script)

real support (with CONFIG_DESKTOP=y): 120+ bytes:
   text	   data	    bss	    dec	    hex	filename
 807958	    624	   7036	 815618	  c7202	busybox_old
 808085	    624	   7036	 815745	  c7281	busybox_unstripped

"fake" support (with CONFIG_DESKTOP unset): ~45 bytes:
   text	   data	    bss	    dec	    hex	filename
 797790	    611	   6996	 805397	  c4a15	busybox_old
 797834	    611	   6996	 805441	  c4a41	busybox_unstripped

3 files changed, 70 insertions, 23 deletions

diff --git a/debianutils/which.c b/debianutils/which.c
index 5ab67194d..41a864cfa 100644
--- a/debianutils/which.c
+++ b/debianutils/which.c
@@ -13,30 +13,69 @@
 #include "libbb.h"
 
 int which_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
-int which_main(int argc, char **argv)
+int which_main(int argc ATTRIBUTE_UNUSED, char **argv)
 {
+        USE_DESKTOP(int opt;)
         int status = EXIT_SUCCESS;
+        char *path;
         char *p;
 
-        if (argc <= 1 || argv[1][0] == '-') {
-                bb_show_usage();
-        }
+        opt_complementary = "-1"; /* at least one argument */
+        USE_DESKTOP(opt =) getopt32(argv, "a");
+        argv += optind;
 
-        /* This matches what is seen on e.g. ubuntu
-         * "which" there is a shell script */
-        if (!getenv("PATH")) {
-                putenv((char*)bb_PATH_root_path);
+        /* This matches what is seen on e.g. ubuntu.
+         * "which" there is a shell script. */
+        path = getenv("PATH");
+        if (!path) {
+                path = (char*)bb_PATH_root_path;
+                putenv(path);
+                path += 5; /* skip "PATH=" */
         }
 
-        while (--argc > 0) {
-                argv++;
+        do {
+#if ENABLE_DESKTOP
+/* Much bloat just to support -a */
                 if (strchr(*argv, '/')) {
                         if (execable_file(*argv)) {
                                 puts(*argv);
                                 continue;
                         }
+                        status = EXIT_FAILURE;
                 } else {
-                        p = find_execable(*argv);
+                        char *path2 = xstrdup(path);
+                        char *tmp = path2;
+
+                        p = find_execable(*argv, &tmp);
+                        if (!p)
+                                status = EXIT_FAILURE;
+                        else {
+ print:
+                                puts(p);
+                                free(p);
+                                if (opt) {
+                                        /* -a: show matches in all PATH components */
+                                        if (tmp) {
+                                                p = find_execable(*argv, &tmp);
+                                                if (p)
+                                                        goto print;
+                                        }
+                                }
+                        }
+                        free(path2);
+                }
+#else
+/* Just ignoring -a */
+                if (strchr(*argv, '/')) {
+                        if (execable_file(*argv)) {
+                                puts(*argv);
+                                continue;
+                        }
+                } else {
+                        char *path2 = xstrdup(path);
+                        char *tmp = path2;
+                        p = find_execable(*argv, &tmp);
+                        free(path2);
                         if (p) {
                                 puts(p);
                                 free(p);
@@ -44,7 +83,8 @@ int which_main(int argc, char **argv)
                         }
                 }
                 status = EXIT_FAILURE;
-        }
+#endif
+        } while (*(++argv) != NULL);
 
         fflush_stdout_and_exit(status);
 }
diff --git a/include/libbb.h b/include/libbb.h
index 492a561a9..1e4968bfa 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -700,7 +700,7 @@ void die_if_bad_username(const char* name);
 #endif
 
 int execable_file(const char *name);
-char *find_execable(const char *filename);
+char *find_execable(const char *filename, char **PATHp);
 int exists_execable(const char *filename);
 
 /* BB_EXECxx always execs (it's not doing NOFORK/NOEXEC stuff),
diff --git a/libbb/execable.c b/libbb/execable.c
index 2649a6cfe..5c2b4505c 100644
--- a/libbb/execable.c
+++ b/libbb/execable.c
@@ -19,15 +19,20 @@ int execable_file(const char *name)
         return (!access(name, X_OK) && !stat(name, &s) && S_ISREG(s.st_mode));
 }
 
-/* search $PATH for an executable file;
+/* search (*PATHp) for an executable file;
  * return allocated string containing full path if found;
- * return NULL otherwise;
+ *  PATHp points to the component after the one where it was found
+ *  (or NULL),
+ *  you may call find_execable again with this PATHp to continue
+ *  (if it's not NULL).
+ * return NULL otherwise; (PATHp is undefined)
+ * in all cases (*PATHp) contents will be trashed (s/:/NUL/).
  */
-char *find_execable(const char *filename)
+char *find_execable(const char *filename, char **PATHp)
 {
-        char *path, *p, *n;
+        char *p, *n;
 
-        p = path = xstrdup(getenv("PATH"));
+        p = *PATHp;
         while (p) {
                 n = strchr(p, ':');
                 if (n)
@@ -35,15 +40,14 @@ char *find_execable(const char *filename)
                 if (*p != '\0') { /* it's not a PATH="foo::bar" situation */
                         p = concat_path_file(p, filename);
                         if (execable_file(p)) {
-                                free(path);
+                                *PATHp = n;
                                 return p;
                         }
                         free(p);
                 }
                 p = n;
-        }
-        free(path);
-        return NULL;
+        } /* on loop exit p == NULL */
+        return p;
 }
 
 /* search $PATH for an executable file;
@@ -52,7 +56,10 @@ char *find_execable(const char *filename)
  */
 int exists_execable(const char *filename)
 {
-        char *ret = find_execable(filename);
+        char *path = xstrdup(getenv("PATH"));
+        char *tmp = path;
+        char *ret = find_execable(filename, &tmp);
+        free(path);
         if (ret) {
                 free(ret);
                 return 1;