busybox: add --uninstall option

Add an option to allow hard links to be removed.

   busybox --uninstall file

removes all hard links to the given file (including the file itself.)
Since Microsoft Windows refuses to delete a running executable a
BusyBox binary is unable to remove links to itself.

   busybox --uninstall -n file

displays the names of all hard links to the given file.

Although this feature is couched in terms of uninstalling BusyBox
it's actually quite general:  it can be used to delete or display
hard links to any file.

1 files changed, 32 insertions, 2 deletions

diff --git a/libbb/appletlib.c b/libbb/appletlib.c
index 11136de11..8a66b3303 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -776,7 +776,8 @@ static void install_links(const char *busybox,
         while (*appname) {
                 fpc = xasprintf("%s/%s.exe", custom_install_dir, appname);
                 rc = link(busybox, fpc);
-                if (rc != 0 && errno != EEXIST) {
+                if (rc != 0 && (errno != EEXIST ||
+                                strcmp("busybox.exe", bb_basename(fpc)) != 0)) {
                         bb_simple_perror_msg(fpc);
                 }
                 free(fpc);
@@ -885,7 +886,13 @@ int busybox_main(int argc UNUSED_PARAM, char **argv)
                         "   or: busybox --show SCRIPT\n"
 #  endif
                         IF_FEATURE_INSTALLER(
-                        "   or: busybox --install "IF_NOT_PLATFORM_MINGW32("[-s] ")"[DIR]\n"
+                        IF_NOT_PLATFORM_MINGW32(
+                        "   or: busybox --install [-s] [DIR]\n"
+                        )
+                        IF_PLATFORM_MINGW32(
+                        "   or: busybox --install [DIR]\n"
+                        "   or: busybox --uninstall [-n] file\n"
+                        )
                         )
                         "   or: function [arguments]...\n"
                         "\n"
@@ -1016,6 +1023,29 @@ int busybox_main(int argc UNUSED_PARAM, char **argv)
                 return 0;
         }
 
+#if ENABLE_PLATFORM_MINGW32 && ENABLE_FEATURE_INSTALLER
+        if (strcmp(argv[1], "--uninstall") == 0) {
+                char name[PATH_MAX];
+                int dry_run = (argv[2] && strcmp(argv[2], "-n") == 0 && ++argv);
+                const char *file = argv[2];
+
+                if (!argv[2])
+                        bb_error_msg_and_die(bb_msg_requires_arg, "--uninstall");
+
+                while (enumerate_links(file, name)) {
+                        if (dry_run) {
+                                full_write1_str(name);
+                                full_write1_str("\n");
+                        }
+                        else if (unlink(name) != 0) {
+                                bb_simple_perror_msg(name);
+                        }
+                        file = NULL;
+                }
+                return 0;
+        }
+#endif
+
         if (strcmp(argv[1], "--help") == 0) {
                 /* "busybox --help [<applet>]" */
                 if (!argv[2])