From 8206db524ca681a973d30eda2098cb943ba2f056 Mon Sep 17 00:00:00 2001
From: Daniel Walter <d.walter@0x90.at>
Date: Tue, 21 Feb 2012 21:39:20 -0600
Subject: update id to be SUS compliant

 * add -n and -G flag
 * allow a username to be given as argument
 * display complete list of groups
 * include it in default build
---
 toys/id.c | 140 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 128 insertions(+), 12 deletions(-)

diff --git a/toys/id.c b/toys/id.c
index 6f0d12fd..6ae3efe5 100644
--- a/toys/id.c
+++ b/toys/id.c
@@ -8,49 +8,165 @@
  *
  * See http://www.opengroup.org/onlinepubs/009695399/utilities/id.html
 
-USE_ID(NEWTOY(id, "gru", TOYFLAG_BIN))
+USE_ID(NEWTOY(id, "nGgru", TOYFLAG_BIN))
 
 config ID
 	bool "id"
-	default n
+	default y
 	help
-	  usage: id [-gru]
+	  usage: id [-nGgru]
 
 	  Print user and group ID.
 
+	  -n	print names instead of numeric IDs (to be used with -Ggu)
+	  -G	Show only the group IDs
 	  -g    Show only the effective group ID
 	  -r	Show real ID instead of effective ID
 	  -u    Show only the effective user ID
 */
 
+#include <sys/types.h>
+#include <pwd.h>
+#include <grp.h>
 #include "toys.h"
 
+#define FLAG_n (1<<4)
+#define FLAG_G (1<<3)
 #define FLAG_g (1<<2)
 #define FLAG_r (1<<1)
 #define FLAG_u 1
 
+void
+pretty_print(struct passwd *pw, struct group *grp, struct group **grps, int n)
+{
+	int i;
+	printf("uid= %d(%s) gid= %d(%s)", pw->pw_uid, pw->pw_name,
+									  grp->gr_gid, grp->gr_name);
+	if (n) {
+		printf(" groups= ");
+	}
+	for (i = 0; i < n; i++) {
+		printf("%d(%s)%s", grps[i]->gr_gid, grps[i]->gr_name,
+						   (i < n-1) ? ",": "");
+	}
+	printf("\n");
+}
+
 void id_main(void)
 {
 	int flags = toys.optflags;
 
+	struct passwd *pw;
+	struct group *grp;
+	struct group **grps;
 	uid_t uid;
 	gid_t gid;
+	gid_t *groups;
+	int i;
+	int ngroups;
+	char *username;
 
-	/* show effective, unless user specifies real */
-	uid = geteuid();
-	gid = getegid();
+	/* check if a username is given */
+	if (*toys.optargs) {
+		username = *(toys.optargs);
+		pw = getpwnam(username);
+		if (!pw) {
+			printf("id: %s: no such user\n", username);
+			toys.exitval = 1;
+			return;
+		}
+		uid = pw->pw_uid;
+		gid = pw->pw_gid;
+	} else {
+		/* show effective, unless user specifies real */
+		if (flags & FLAG_r) {
+			uid = getuid();
+			gid = getgid();
+		} else {
+			uid = geteuid();
+			gid = getegid();
+		}
+	}
 
-	if (flags & FLAG_r) {
-		uid = getuid();
-		gid = getgid();
+	pw = getpwuid(uid);
+	if (!pw) {
+		perror("id");
+		toys.exitval = 1;
+		return;
+	}
+	
+	grp = getgrgid(pw->pw_gid);
+	if (!grp) {
+		perror("id");
+		toys.exitval = 1;
+		return;
 	}
+	
 	if (flags & FLAG_u) {
-	    printf("%d\n", uid);
+		if (flags & FLAG_n)
+		    printf("%s\n", pw->pw_name);
+		else
+		    printf("%d\n", pw->pw_uid);
 		return;
 	}
 	if (flags & FLAG_g) {
-		printf("%d\n", gid);
+		if (flags & FLAG_n)
+			printf("%s\n", grp->gr_name);
+		else
+			printf("%d\n", grp->gr_gid);
 		return;
 	}
-	printf("%d %d\n", uid, gid);
+	
+
+	if (flags & FLAG_r) {
+		printf("-r can only be used in combination with -u or -g\n");
+		toys.exitval = 1;
+		return;
+	}
+	ngroups = sysconf(_SC_NGROUPS_MAX);
+	/* fallback for number of groups to 32 */
+	if (ngroups < 0)
+		ngroups = 32;
+	groups = malloc(ngroups * sizeof(gid_t));
+	if (!groups) {
+		perror("id");
+		toys.exitval = 1;
+		return;
+	}
+	if (getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups) < 0) {
+		perror("id");
+		toys.exitval = 1;
+		return;
+	}
+	grps = malloc(ngroups * sizeof(struct group *));
+	for (i = 0; i < ngroups; i++) {
+		struct group *tmp;
+		grps[i] = malloc(sizeof(struct group));
+		size_t f = sysconf(_SC_GETGR_R_SIZE_MAX);
+		char *buf = malloc(f);
+		if (getgrgid_r(groups[i], grps[i], buf, f, &tmp) < 0) {
+			perror("id");
+			continue;
+		}
+		if (tmp == NULL) {
+			perror("id");
+			continue;
+		}
+	}
+	
+	if (flags & FLAG_G) {
+		for (i = 0; i < ngroups; i++) {
+			if (flags & FLAG_n)
+				printf("%s%s", !i ? "" : " ", grps[i]->gr_name);
+			else
+				printf("%s%d", !i ? "" : " ", grps[i]->gr_gid);
+		}
+		printf("\n");
+		return;
+	}
+
+	pretty_print(pw, grp, grps, ngroups);
+	for (i=0; i < ngroups; i++)
+		free(grps[i]);
+
 }
-- 
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