From 28e26bc6887410d10b454ec7d98d93cc5d4434eb Mon Sep 17 00:00:00 2001
From: Tai Chi Minh Ralph Eastwood <tcmreastwood@gmail.com>
Date: Wed, 11 Feb 2015 08:55:17 +0000
Subject: [PATCH] readlink: add -m and -f flags

---
 readlink.c | 68 +++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 54 insertions(+), 14 deletions(-)

diff --git a/readlink.c b/readlink.c
index 9c1479a..1089d06 100644
--- a/readlink.c
+++ b/readlink.c
@@ -5,6 +5,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/stat.h>
 
 #include "util.h"
 
@@ -17,17 +18,18 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
-	char buf[PATH_MAX];
+	char buf1[PATH_MAX], buf2[PATH_MAX], arg[PATH_MAX];
 	int nflag = 0;
-	int fflag = 0;
+	int mefflag = 0;
 	ssize_t n;
+	struct stat st;
+	char *p = arg, *lp = NULL, *b = buf1;
 
 	ARGBEGIN {
-	case 'e':
 	case 'm':
-		eprintf("not implemented\n");
+	case 'e':
 	case 'f':
-		fflag = 1;
+		mefflag = ARGC();
 		break;
 	case 'n':
 		nflag = 1;
@@ -42,16 +44,54 @@ main(int argc, char *argv[])
 	if (strlen(argv[0]) > PATH_MAX - 1)
 		eprintf("path too long\n");
 
-	if (fflag) {
-		if (!realpath(argv[0], buf))
-			exit(1);
-	} else {
-		if ((n = readlink(argv[0], buf, sizeof(buf) - 1)) < 0)
-			exit(1);
-		buf[n] = '\0';
+#define SWAP_BUF() (b = (b == buf1 ? buf2 : buf1));
+	switch (mefflag) {
+		case 'm':
+			if (argv[0][0] == '/') { /* case when path is on '/' */
+				arg[0] = '/';
+				arg[1] = '\0';
+				p++;
+			} else if (!strchr(argv[0], '/')) { /* relative path */
+				arg[0] = '.';
+				arg[1] = '/';
+				arg[2] = '\0';
+			} else
+				arg[0] = '\0';
+			strncat(arg, argv[0], PATH_MAX);
+			while ((p = strchr(p, '/'))) {
+				*p = '\0';
+				if (!realpath(arg, b)) {
+					*p = '/';
+					goto mdone;
+				}
+				SWAP_BUF();
+				lp = p;
+				*p++ = '/';
+			}
+			if (!realpath(arg, b)) {
+mdone:
+				SWAP_BUF();
+				if (lp) {
+					/* drop the extra '/' on root */
+					lp += (argv[0][0] == '/' &&
+					       lp - arg == 1);
+					strncat(b, lp, PATH_MAX);
+				}
+			}
+			break;
+		case 'e':
+			if (stat(argv[0], &st) < 0)
+				exit(1);
+		case 'f':
+			if (!realpath(argv[0], b))
+				exit(1);
+			break;
+		default:
+			if ((n = readlink(argv[0], b, PATH_MAX - 1)) < 0)
+				exit(1);
+			b[n] = '\0';
 	}
-
-	printf("%s", buf);
+	printf("%s", b);
 	if (!nflag)
 		putchar('\n');