add more features

id/id.c

@@ -0,0 +1,66 @@
+#include <limits.h> /* LOGIN_NAME_MAX */
+#include <stdbool.h>
+#include <stdio.h> /* fprintf(3) */
+#include <stdlib.h> /* stderr, stdout */
+#include <sysexits.h>
+#include <unistd.h> /* getuid(2), geteuid(2), getopt(3) */
+#include "usefulmacros.h"
+
+int main(int argc, char *argv[]){
+	int c;
+	char mode;
+	bool n;
+	char name[LOGIN_NAME_MAX];
+	bool r;
+	uid_t euid;
+	uid_t uid;
+
+	NOARGVZERO(argv);
+
+	mode = 0;
+	n = false;
+	r = false;
+
+	while((c = getopt(argc, argv, "Gghnru")) != -1)
+		switch(c){
+		case 'G': case 'g': case 'u':
+			if(mode == 0){
+				mode = c;
+				break;
+			}
+			/* FALLTHROUGH */
+		case 'h': default: usage:
+			fprintf(stderr, "Usage: %s [-G]|[-g]|[-u] (-rn) (user)\n", argv[0]);
+			return EX_USAGE;
+		case 'n':
+			n = true;
+			break;
+		case 'r':
+			r = true;
+			break;
+		}
+	
+	switch(mode){
+		case 0:
+			goto usage;
+		case 'G':
+		case 'g':
+			return EX_SOFTWARE;
+		case 'u':
+			euid = geteuid();
+			uid = getuid();
+			if(!n){
+				if(r || euid != uid)
+					fprintf(stdout, "%u\n", uid);
+				if(!r)
+					fprintf(stdout, "%u\n", euid);
+			}else
+				{}
+				/* Both busybox and GNU coreutils (according to straces) parse passwd(5)
+				 * for this. TODO. */
+			break;
+		default:
+			return EX_SOFTWARE;
+	}
+	return EX_OK;
+}