From 3e5a6644c8cbbfa43be070b34c770b0fb620523d Mon Sep 17 00:00:00 2001
From: Jonas 'Sortie' Termansen <sortie@maxsi.org>
Date: Wed, 16 Oct 2013 20:17:45 +0200
Subject: [PATCH] Improve implementation of pwd(1).

---
 utils/pwd.cpp | 123 +++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 117 insertions(+), 6 deletions(-)

diff --git a/utils/pwd.cpp b/utils/pwd.cpp
index e7fc50cf..ed02c931 100644
--- a/utils/pwd.cpp
+++ b/utils/pwd.cpp
@@ -1,6 +1,6 @@
 /*******************************************************************************
 
-    Copyright(C) Jonas 'Sortie' Termansen 2012.
+    Copyright(C) Jonas 'Sortie' Termansen 2013.
 
     This program is free software: you can redistribute it and/or modify it
     under the terms of the GNU General Public License as published by the Free
@@ -20,14 +20,125 @@
 
 *******************************************************************************/
 
+#include <errno.h>
+#include <error.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 #include <unistd.h>
 
-int main(int /*argc*/, char* /*argv*/[])
+#if !defined(VERSIONSTR)
+#define VERSIONSTR "unknown version"
+#endif
+
+static bool nul_or_slash(char c)
 {
-	const size_t WDSIZE = 4096;
-	char wd[WDSIZE];
-	if ( !getcwd(wd, WDSIZE) ) { perror("getcwd"); return 1; }
-	printf("%s\n", wd);
+	return !c || c == '/';
+}
+
+static bool next_elem_is_dot_or_dot_dot(const char* path)
+{
+	return (path[0] == '.' && nul_or_slash(path[1])) ||
+	       (path[0] == '.' && path[1] == '.' && nul_or_slash(path[2]));
+}
+
+static bool is_path_absolute(const char* path)
+{
+	size_t index = 0;
+	if ( path[index++] != '/' )
+		return false;
+	while ( path[index] )
+	{
+		if ( next_elem_is_dot_or_dot_dot(path) )
+			return false;
+		while ( !nul_or_slash(path[index]) )
+			index++;
+		if ( path[index] == '/' )
+			index++;
+	}
+	return true;
+}
+
+static void usage(FILE* fp, const char* argv0)
+{
+	fprintf(fp, "Usage: %s [OPTION]...\n", argv0);
+	fprintf(fp, "Print the full filename of the current working directory.\n");
+	fprintf(fp, "\n");
+	fprintf(fp, "  -L, --logical   use PWD from environment, even if it contains symlinks\n");
+	fprintf(fp, "  -P, --physical  avoid all symlinks\n");
+	fprintf(fp, "      --help      display this help and exit\n");
+	fprintf(fp, "      --usage     display this help and exit\n");
+	fprintf(fp, "      --version   output version information and exit\n");
+}
+
+static void help(FILE* fp, const char* argv0)
+{
+	usage(fp, argv0);
+}
+
+static void version(FILE* fp, const char* argv0)
+{
+	fprintf(fp, "%s (Sortix) %s\n", argv0, VERSIONSTR);
+	fprintf(fp, "License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.\n");
+	fprintf(fp, "This is free software: you are free to change and redistribute it.\n");
+	fprintf(fp, "There is NO WARRANTY, to the extent permitted by law.\n");
+}
+
+int main(int argc, char* argv[])
+{
+	const char* argv0 = argv[0];
+	bool physical = false;
+	for ( int i = 0; i < argc; i++ )
+	{
+		const char* arg = argv[i];
+		if ( arg[0] != '-' || !arg[1] )
+			continue;
+		argv[i] = NULL;
+		if ( !strcmp(arg, "--") )
+			break;
+		if ( arg[1] != '-' )
+		{
+			while ( char c = *++arg ) switch ( c )
+			{
+			case 'L': physical = false; break;
+			case 'P': physical = true; break;
+			default:
+				fprintf(stderr, "%s: unknown option -- '%c'\n", argv0, c);
+				usage(stderr, argv0);
+				exit(1);
+			}
+		}
+		else if ( !strcmp(arg, "--help") )
+			help(stdout, argv0), exit(0);
+		else if ( !strcmp(arg, "--usage") )
+			usage(stdout, argv0), exit(0);
+		else if ( !strcmp(arg, "--version") )
+			version(stdout, argv0), exit(0);
+		else if ( !strcmp(arg, "--logical") )
+			physical = false;
+		else if ( !strcmp(arg, "--physical") )
+			physical = true;
+		else
+		{
+			fprintf(stderr, "%s: unknown option: %s\n", argv0, arg);
+			usage(stderr, argv0);
+			exit(1);
+		}
+	}
+
+	// The get_current_dir_name function will use the PWD variable if it is
+	// accurate, so we'll need to unset it if it is inappropriate to use it.
+	if ( const char* pwd = getenv("PWD") )
+	{
+		if ( physical || !is_path_absolute(pwd) )
+			unsetenv(pwd);
+	}
+
+	char* pwd = get_current_dir_name();
+	if ( !pwd )
+		error(1, errno, "get_current_dir_name");
+
+	printf("%s\n", pwd);
+
 	return 0;
 }