Add env(1).

doc/user-guide

@@ -157,6 +157,7 @@ Sortix comes with a number of home-made programs. Here is an overview:
 * `du` - report file and directory disk usage
 * `echo` - print command line arguments
 * `editor` - text editor
+* `env` - run a program in a modified environment
 * `extfs` - ext2 filesystem server
 * `false` - exit with an error status
 * `find` - recursively list files

utils/.gitignore

@@ -12,6 +12,7 @@ date
 du
 echo
 editor
+env
 false
 find
 head

utils/Makefile

@@ -28,6 +28,7 @@ date \
 du \
 echo \
 editor \
+env \
 false \
 find \
 head \

utils/env.cpp

@@ -0,0 +1,209 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2014.
+
+    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/>.
+
+    env.cpp
+    Set the environment for command invocation.
+
+*******************************************************************************/
+
+#include <errno.h>
+#include <error.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+void clean_environment()
+{
+	while ( environ[0] )
+	{
+		size_t equal_pos = strcspn(environ[0], "=");
+		if ( environ[0][equal_pos] != '=' )
+			error(125, 0, "Bad Environment");
+		char* key = strndup(environ[0], equal_pos);
+		if ( !key )
+			error(125, errno, "strndup");
+		if ( unsetenv(key) != 0 )
+			error(125, errno, "cannot unset `%s'", key);
+		free(key);
+	}
+}
+
+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]... [-] [NAME=VALUE]... [COMMAND [ARG]...]\n", argv0);
+	fprintf(fp, "Set each NAME to VALUE in the environment and run COMMAND.\n");
+	fprintf(fp, "\n");
+	fprintf(fp, "  -i, --ignore-environment  start with an empty environment\n");
+	fprintf(fp, "  -0, --null           end each output line with 0 byte rather than newline\n");
+	fprintf(fp, "  -u, --unset=NAME     remove variable from the environment\n");
+	fprintf(fp, "      --help           display this help and exit\n");
+	fprintf(fp, "      --version        output version information and exit\n");
+	fprintf(fp, "\n");
+	fprintf(fp, "A mere - implies -i.  If no COMMAND, print the resulting environment.\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[])
+{
+	bool ignore_environment = false;
+	bool null_terminate = false;
+
+	const char* argv0 = argv[0];
+	for ( int i = 1; i < argc; i++ )
+	{
+		const char* arg = argv[i];
+		if ( arg[0] != '-' )
+			break;
+		if ( arg[0] == '-' && !arg[1] )
+		{
+			ignore_environment = true;
+			break;
+		}
+		argv[i] = NULL;
+		if ( !strcmp(arg, "--") )
+			break;
+		if ( arg[1] != '-' )
+		{
+			while ( char c = *++arg ) switch ( c )
+			{
+			case 'i': ignore_environment = true; break;
+			case 'u':
+				if ( !arg[1] )
+				{
+					if ( i + 1 == argc )
+					{
+						error(0, 0, "option requires an argument -- 'u'");
+						fprintf(stderr, "Try `%s --help' for more information.\n", argv[0]);
+						exit(125);
+					}
+					const char* key = argv[i+1];
+					argv[++i] = NULL;
+					if ( unsetenv(key) != 0 )
+						error(125, errno, "cannot unset `%s'", key);
+				}
+				else
+				{
+					const char* key = arg + 1;
+					if ( unsetenv(key) != 0 )
+						error(125, errno, "cannot unset `%s'", key);
+				}
+				arg = "u";
+				break;
+			case '0': null_terminate = true; break;
+			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, "--ignore-environment") )
+			ignore_environment = true;
+		else if ( !strcmp(arg, "--null") )
+			null_terminate = true;
+		else if ( !strncmp(arg, "--unset=", strlen("--unset=")) )
+		{
+			const char* key = arg + strlen("--unset=");
+			if ( unsetenv(key) != 0 )
+				error(125, errno, "cannot unset `%s'", key);
+		}
+		else if ( !strcmp(arg, "--unset") )
+		{
+			if ( i + 1 == argc )
+			{
+				error(0, 0, "option '--unset' requires an argument");
+				fprintf(stderr, "Try `%s --help' for more information.\n", argv[0]);
+				exit(125);
+			}
+			const char* key = argv[i+1];
+			argv[++i] = NULL;
+			if ( unsetenv(key) != 0 )
+				error(125, errno, "cannot unset `%s'", key);
+		}
+		else
+		{
+			fprintf(stderr, "%s: unknown option: %s\n", argv0, arg);
+			help(stderr, argv0);
+			exit(1);
+		}
+	}
+
+	if ( ignore_environment )
+		clean_environment();
+
+	compact_arguments(&argc, &argv);
+
+	for ( int i = 1; i < argc; i++ )
+	{
+		char* arg = argv[i];
+		size_t equal_pos = strcspn(arg, "=");
+		if ( arg[equal_pos] != '=' )
+			break;
+		argv[i] = NULL;
+		arg[equal_pos] = '\0';
+		const char* key = arg;
+		const char* value = arg + equal_pos + 1;
+		if ( setenv(key, value, 1) != 0 )
+			error(125, errno, "setenv(\"%s\", \"%s\")", key, value);
+	}
+
+	compact_arguments(&argc, &argv);
+
+	if ( argc == 1 )
+	{
+		for ( size_t i = 0; environ[i]; i++ )
+		{
+			fputs(environ[i], stdout);
+			fputc(null_terminate ? '\0' : '\n', stdout);
+		}
+		return 0;
+	}
+
+	if ( null_terminate )
+	{
+		error(0, 0, "cannot specify --null (-0) with command");
+		fprintf(stderr, "Try `%s --help' for more information.\n", argv[0]);
+		exit(125);
+	}
+
+	execvp(argv[1], argv + 1);
+	error(errno == ENOENT ? 127 : 126, errno, "%s", argv[1]);
+}

utils/sh.cpp

@@ -339,13 +339,6 @@ readcmd:
 		}
 	}
 
-	if ( !strcmp(argv[0], "env") )
-	{
-		for ( size_t i = 0; environ[i]; i++ )
-			printf("%s\n", environ[i]);
-		exit(0);
-	}
-
 	execvp(argv[0], argv);
 	if ( interactive )
 	{