jimsh: Allow option "--help" and enable place for parsing other options in future

1 files changed, 27 insertions, 1 deletions

diff --git a/jimsh.c b/jimsh.c
index fe89649..afcd7dd 100644
--- a/jimsh.c
+++ b/jimsh.c
@@ -65,15 +65,38 @@ static void JimPrintErrorMessage(Jim_Interp *interp)
     fprintf(stderr, "%s\n", Jim_String(Jim_GetResult(interp)));
 }
 
+void usage(const char* executable_name)
+{
+    printf("jimsh version %d.%d\n", JIM_VERSION / 100, JIM_VERSION % 100);
+    printf("Usage: %s\n", executable_name);
+    printf("or   : %s [options] [filename]\n", executable_name);
+    printf("\n");
+    printf("Without options: Interactive mode\n");
+    printf("\n");
+    printf("Options:\n");
+    printf("         --version  : prints the version string\n");
+    printf("         --help     : prints this text\n");
+    printf("         -e CMD     : executes command CMD\n");
+    printf("                      NOTE: all subsequent options will be passed as arguments to the command\n");
+    printf("         [filename] : executes the script contained in the named file\n");
+    printf("                      NOTE: all subsequent options will be passed to the script\n\n");
+}
+
 int main(int argc, char *const argv[])
 {
     int retcode;
     Jim_Interp *interp;
+    char *const orig_argv0 = argv[0];
 
+    /* Parse initial arguments before interpreter is started */
     if (argc > 1 && strcmp(argv[1], "--version") == 0) {
         printf("%d.%d\n", JIM_VERSION / 100, JIM_VERSION % 100);
         return 0;
     }
+    else if (argc > 1 && strcmp(argv[1], "--help") == 0) {
+        usage(argv[0]);
+        return 0;
+    }
 
     /* Create and initialize the interpreter */
     interp = Jim_CreateInterp();
@@ -84,11 +107,12 @@ int main(int argc, char *const argv[])
         JimPrintErrorMessage(interp);
     }
 
-    Jim_SetVariableStrWithStr(interp, "jim::argv0", argv[0]);
+    Jim_SetVariableStrWithStr(interp, "jim::argv0", orig_argv0);
     Jim_SetVariableStrWithStr(interp, JIM_INTERACTIVE, argc == 1 ? "1" : "0");
     retcode = Jim_initjimshInit(interp);
 
     if (argc == 1) {
+        /* Executable name is the only argument - start interactive prompt */
         if (retcode == JIM_ERR) {
             JimPrintErrorMessage(interp);
         }
@@ -98,7 +122,9 @@ int main(int argc, char *const argv[])
         }
     }
     else {
+        /* Additional arguments - interpret them */
         if (argc > 2 && strcmp(argv[1], "-e") == 0) {
+            /* Evaluate code in subsequent argument */
             JimSetArgv(interp, argc - 3, argv + 3);
             retcode = Jim_Eval(interp, argv[2]);
             if (retcode != JIM_ERR) {