which,ash: changes to which/command/type

Change how 'which' detects if it was run from a standalone shell:
the shell passes the undocumented '-s' option.  This is stricter
and more reliable than the previous method of checking the name
of the binary.

Add a function to determine the binary associated with a given
applet name.  This makes it possible for 'which' and 'command -v'
to list the correct binary even for applets other than 'busybox'.
For example, when the binary is called 'sh.exe' 'which sh' will
report its path.

In standalone shell mode 'command -V' and 'type' now report "xxx
is a builtin applet" rather than "xxx is xxx", which is true but
not very illuminating.

(GitHub issue #248)

1 files changed, 16 insertions, 2 deletions

diff --git a/shell/ash.c b/shell/ash.c
index afb865146..97075ed5f 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -8904,6 +8904,16 @@ tryexec(IF_FEATURE_SH_STANDALONE(int applet_no,) const char *cmd, char **argv, c
                                 (fs && fs->fpid == FS_SHELLEXEC)) {
                         /* mingw-w64's getopt() uses __argv[0] as the program name */
                         __argv[0] = (char *)cmd;
+                        /* 'which' wants to know if it was invoked from a standalone
+                         * shell.  Use the spare element of argv to add a flag, but
+                         * not if the first argument is '--help', that's a special
+                         * case. */
+                        if (strcmp(argv[0], "which") == 0 &&
+                                        (argv[1] == NULL || strcmp(argv[1], "--help") != 0)) {
+                                --argv;
+                                argv[0] = argv[1];
+                                argv[1] = (char *)"-s";
+                        }
 # else
                 if (APPLET_IS_NOEXEC(applet_no)) {
 # endif
@@ -9456,7 +9466,12 @@ describe_command(char *command, const char *path, int describe_command_verbose)
 #if ENABLE_PLATFORM_MINGW32 && ENABLE_FEATURE_SH_STANDALONE
                 if (j < -1) {
                         p = (char *)bb_basename(command);
-                        goto describe;
+                        if (describe_command_verbose) {
+                                out1fmt(" is a builtin applet");
+                        } else {
+                                out1str(applet_to_exe(p));
+                        }
+                        break;
                 }
 #endif
                 if (j < 0) {
@@ -9474,7 +9489,6 @@ describe_command(char *command, const char *path, int describe_command_verbose)
 #if ENABLE_PLATFORM_MINGW32
                 add_win32_extension(p);
                 bs_to_slash(p);
- IF_FEATURE_SH_STANDALONE(describe:)
 #endif
                 if (describe_command_verbose) {
                         out1fmt(" is %s", p);