From fad6b54c1c84031291b76644aa9d944ec1dcd091 Mon Sep 17 00:00:00 2001
From: Rob Pilling <robpilling@gmail.com>
Date: Sun, 1 Dec 2013 11:40:49 +0000
Subject: [PATCH 2/2] id(1) can handle uid arguments

---
 id.1 |    6 +++---
 id.c |   51 ++++++++++++++++++++++++++++++++++++---------------
 2 files changed, 39 insertions(+), 18 deletions(-)

diff --git a/id.1 b/id.1
index 8252773..6bfa06b 100644
--- a/id.1
+++ b/id.1
@@ -3,10 +3,10 @@
 id \- print real and effective user and group IDs
 .SH SYNOPSIS
 .B id
-.RB [ user ]
+.RB [ user | uid ]
 .SH DESCRIPTION
 Print user and group information of the calling process to standard output.
-If a login name is specified, the user and group information of that user
-is displayed.
+If a login name or uid is specified, the user and group information of that
+user is displayed.
 .SH SEE ALSO
 .IR who(1)
diff --git a/id.c b/id.c
index ce618fd..78fa71d 100644
--- a/id.c
+++ b/id.c
@@ -7,21 +7,22 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <limits.h>
+#include <ctype.h>
 #include "util.h"
 
 static void user(struct passwd *pw);
+static void userid(uid_t id);
+static void usernam(const char *nam);
 
 static void
 usage(void)
 {
-	eprintf("usage: %s [user]\n", argv0);
+	eprintf("usage: %s [user | uid]\n", argv0);
 }
 
 int
 main(int argc, char *argv[])
 {
-	struct passwd *pw;
-
 	ARGBEGIN {
 	default:
 		usage();
@@ -30,20 +31,14 @@ main(int argc, char *argv[])
 	errno = 0;
 	switch (argc) {
 	case 0:
-		pw = getpwuid(getuid());
-		if (errno != 0)
-			eprintf("getpwuid %d:", getuid());
-		else if (!pw)
-			eprintf("getpwuid %d: no such user\n", getuid());
-		user(pw);
+		userid(getuid());
 		break;
 	case 1:
-		pw = getpwnam(argv[0]);
-		if (errno != 0)
-			eprintf("getpwnam %s:", argv[0]);
-		else if (!pw)
-			eprintf("getpwnam %s: no such user\n", argv[0]);
-		user(pw);
+		/* user names can't begin [0-9] */
+		if (isdigit(argv[0][0]))
+			userid(estrtol(argv[0], 0));
+		else
+			usernam(argv[0]);
 		break;
 	default:
 		usage();
@@ -52,6 +47,32 @@ main(int argc, char *argv[])
 	return EXIT_SUCCESS;
 }
 
+static void usernam(const char *nam)
+{
+	struct passwd *pw;
+
+	errno = 0;
+	pw = getpwnam(nam);
+	if (errno != 0)
+		eprintf("getpwnam %s:", nam);
+	else if (!pw)
+		eprintf("getpwnam %s: no such user\n", nam);
+	user(pw);
+}
+
+static void userid(uid_t id)
+{
+	struct passwd *pw;
+
+	errno = 0;
+	pw = getpwuid(id);
+	if (errno != 0)
+		eprintf("getpwuid %d:", id);
+	else if (!pw)
+		eprintf("getpwuid %d: no such user\n", id);
+	user(pw);
+}
+
 static void
 user(struct passwd *pw)
 {
-- 
1.7.10.4