Add realpath(1).

doc/user-guide

@@ -189,6 +189,7 @@ Sortix comes with a number of home-made programs. Here is an overview:
 * `mv` - move a file
 * `pager` - display file page by page
 * `pwd` - print current directory path
+* `realpath` - canonicalize filesystem paths
 * `regress` - run system tests
 * `rm` - remove file
 * `rmdir` - remove empty directory

utils/.gitignore

@@ -30,6 +30,7 @@ mktemp
 mv
 pager
 pwd
+realpath
 rm
 rmdir
 sleep

utils/Makefile

@@ -42,6 +42,7 @@ mktemp \
 mv \
 pager \
 pwd \
+realpath \
 rm \
 rmdir \
 sleep \

utils/realpath.cpp

@@ -0,0 +1,114 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2015.
+
+    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
+    Software Foundation, either version 3 of the License, or (at your option)
+    any later version.
+
+    This program is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+    more details.
+
+    You should have received a copy of the GNU General Public License along with
+    this program. If not, see <http://www.gnu.org/licenses/>.
+
+    realpath.cpp
+    Canonicalize filesystem paths.
+
+*******************************************************************************/
+
+#include <errno.h>
+#include <error.h>
+#include <locale.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static void compact_arguments(int* argc, char*** argv)
+{
+	for ( int i = 0; i < *argc; i++ )
+	{
+		while ( i < *argc && !(*argv)[i] )
+		{
+			for ( int n = i; n < *argc; n++ )
+				(*argv)[n] = (*argv)[n+1];
+			(*argc)--;
+		}
+	}
+}
+
+static void help(FILE* fp, const char* argv0)
+{
+	fprintf(fp, "Usage: %s [OPTION]... PATH...\n", argv0);
+	fprintf(fp, "Convert the paths to canonicalized absolute paths.\n");
+}
+
+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[])
+{
+	setlocale(LC_ALL, "");
+
+	int eol = '\n';
+	const char* argv0 = argv[0];
+	for ( int i = 1; 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 'z': eol = '\0';
+			default:
+				fprintf(stderr, "%s: unknown option -- '%c'\n", argv0, c);
+				help(stderr, argv0);
+				exit(1);
+			}
+		}
+		else if ( !strcmp(arg, "--help") )
+			help(stdout, argv0), exit(0);
+		else if ( !strcmp(arg, "--version") )
+			version(stdout, argv0), exit(0);
+		else if ( !strcmp(arg, "--zero") )
+			eol = '\0';
+		else
+		{
+			fprintf(stderr, "%s: unknown option: %s\n", argv0, arg);
+			help(stderr, argv0);
+			exit(1);
+		}
+	}
+
+	compact_arguments(&argc, &argv);
+
+	int result = 0;
+	for ( int i = 1; i < argc; i++ )
+	{
+		char* path = realpath(argv[i], NULL);
+		if ( !path )
+		{
+			error(0, errno, "%s", argv[i]);
+			result = 1;
+			continue;
+		}
+		fputs(path, stdout);
+		putchar(eol);
+		free(path);
+	}
+
+	return result;
+}