Add id(1).

doc/user-guide

@@ -173,6 +173,7 @@ Sortix comes with a number of home-made programs. Here is an overview:
 * `find` - recursively list files
 * `head` - display start of file
 * `help` - show list of available programs
+* `id` - print real and effective user and group IDs
 * `init` - system management deamon
 * `initrdfs` - tool for examining initrds
 * `install` - installs a program into a system directory

utils/.gitignore

@@ -18,6 +18,7 @@ expr
 false
 find
 head
+id
 help
 kernelinfo
 kill

utils/Makefile

@@ -31,6 +31,7 @@ false \
 find \
 head \
 help \
+id \
 kernelinfo \
 kill \
 ln \

utils/id.cpp

@@ -0,0 +1,240 @@
+/*******************************************************************************
+
+    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/>.
+
+    id.cpp
+    Return user identity.
+
+*******************************************************************************/
+
+#include <sys/types.h>
+
+#include <err.h>
+#include <errno.h>
+#include <grp.h>
+#include <locale.h>
+#include <pwd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+const char* name_of_group_by_gid(gid_t gid)
+{
+	errno = 0;
+	struct group* grp = getgrgid(gid);
+	if ( !grp && errno == 0 )
+		errx(1, "gid %" PRIuGID " has no group entry", gid);
+	if ( !grp )
+		err(1, "gid %" PRIuGID "", gid);
+	return grp->gr_name;
+}
+
+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]... [USERNAME]\n", argv0);
+	fprintf(fp, "Print user and group information for the specified USERNAME,\n");
+	fprintf(fp, "or (when USERNAME omitted) for the current user.\n");
+	fprintf(fp, "\n");
+	fprintf(fp, "  -g, --group    print only the effective group ID\n");
+	fprintf(fp, "  -G, --groups   print all group IDs\n");
+	fprintf(fp, "  -n, --name     print a name instead of a number, for -ugG\n");
+	fprintf(fp, "  -r, --real     print the real ID instead of the effective ID, with -ugG\n");
+	fprintf(fp, "  -u, --user     print only the effective user ID\n");
+	fprintf(fp, "      --help     display this help and exit\n");
+	fprintf(fp, "      --version  output version information and exit\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, "");
+
+	bool groups_only = false;
+	bool group_only = false;
+	bool user_only = false;
+	bool names = false;
+	bool real = false;
+
+	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 'G': groups_only = true; break;
+			case 'g': group_only = true; break;
+			case 'n': names = true; break;
+			case 'r': real = true; break;
+			case 'u': user_only = true; break;
+			default:
+				fprintf(stderr, "%s: unknown option -- '%c'\n", argv0, c);
+				help(stderr, argv0);
+				exit(1);
+			}
+		}
+		else if ( !strcmp(arg, "--group") )
+			group_only = true;
+		else if ( !strcmp(arg, "--groups") )
+			groups_only = true;
+		else if ( !strcmp(arg, "--name") )
+			names = true;
+		else if ( !strcmp(arg, "--real") )
+			real = true;
+		else if ( !strcmp(arg, "--user") )
+			user_only = true;
+		else if ( !strcmp(arg, "--help") )
+			help(stdout, argv0), exit(0);
+		else if ( !strcmp(arg, "--version") )
+			version(stdout, argv0), exit(0);
+		else
+		{
+			fprintf(stderr, "%s: unknown option: %s\n", argv0, arg);
+			help(stderr, argv0);
+			exit(1);
+		}
+	}
+
+	compact_arguments(&argc, &argv);
+
+	if ( 1 < groups_only + group_only + user_only )
+		errx(1, "options -Ggu are mutually exclusive");
+
+	(void) real; // Sortix only has real user ids.
+
+	struct passwd* pwd;
+	if ( 2 < argc )
+		errx(1, "extra operand '%s'", argv[2]);
+	else if ( argc == 2 )
+	{
+		errno = 0;
+		pwd = getpwnam(argv[1]);
+		if ( !pwd && errno == 0 )
+			errx(1, "%s: no such user", argv[1]);
+		if ( !pwd )
+			err(1, "%s", argv[1]);
+	}
+	else
+	{
+		errno = 0;
+		pwd = getpwuid(getuid());
+		if ( !pwd && errno == 0 )
+			errx(1, "current user has no user entry");
+		if ( !pwd )
+			err(1, "current user");
+	}
+
+	if ( groups_only )
+	{
+		// TODO: Sortix doesn't have getgroups at the moment.
+		if ( names )
+			printf("%s", name_of_group_by_gid(pwd->pw_gid));
+		else
+			printf("%" __PRIuGID, pwd->pw_gid);
+		setgrent();
+		struct group* grp;
+		while ( (errno = 0, grp = getgrent()) )
+		{
+			if ( grp->gr_gid == pwd->pw_gid )
+				continue;
+			bool member = false;
+			for ( size_t i = 0; !member && grp->gr_mem[i]; i++ )
+				member = !strcmp(pwd->pw_name, grp->gr_mem[i]);
+			if ( !member )
+				continue;
+			if ( names )
+				printf(" %s", grp->gr_name);
+			else
+				printf(" %" __PRIuGID "", grp->gr_gid);
+		}
+		if ( errno != 0 )
+			err(1, "getgrent");
+		endgrent();
+		printf("\n");
+	}
+	else if ( group_only )
+	{
+		// If current user, should this display the getgid() group instead?
+		if ( names )
+			printf("%s\n", name_of_group_by_gid(pwd->pw_gid));
+		else
+			printf("%" __PRIuGID "\n", pwd->pw_gid);
+	}
+	else if ( user_only )
+	{
+		if ( names )
+			printf("%s\n", pwd->pw_name);
+		else
+			printf("%" __PRIuUID "\n", pwd->pw_uid);
+	}
+	else
+	{
+		if ( names || real )
+			errx(1, "cannot print only names or real IDs in default format");
+		name_of_group_by_gid(pwd->pw_gid); // Early error.
+		printf("uid=%" PRIuUID "(%s) ", pwd->pw_uid, pwd->pw_name);
+		printf("gid=%" PRIiGID "(%s) ", pwd->pw_gid, name_of_group_by_gid(pwd->pw_gid));
+		printf("groups=");
+		const char* prefix = "";
+		setgrent();
+		struct group* grp;
+		while ( (errno = 0, grp = getgrent()) )
+		{
+			bool member = false;
+			for ( size_t i = 0; !member && grp->gr_mem[i]; i++ )
+				member = !strcmp(pwd->pw_name, grp->gr_mem[i]);
+			if ( !member )
+				continue;
+			printf("%s%" __PRIuGID "(%s)", prefix, grp->gr_gid, grp->gr_name);
+			prefix = ",";
+		}
+		if ( errno != 0 )
+			err(1, "getgrent");
+		endgrent();
+		printf("\n");
+	}
+
+	if ( ferror(stdout) || fflush(stdout) == EOF )
+		return 1;
+	return 0;
+}