Utilities: Add groupadd

Base/usr/share/man/man8/groupadd.md

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+## Name
+
+groupadd - add a new group to the system group file
+
+## Synopsis
+
+```**sh
+# groupadd [options] <group>
+```
+
+## Description
+
+This program adds a new group to the system.
+
+This program must be run as root.
+
+## Options
+
+* `-g`, `--gid` _gid_: The group identifier for the new group. If not specified, an unused GID above `100` will be auto-generated.
+
+## Exit Values
+
+* 0 - Success
+* 1 - Couldn't update the group file
+* 3 - Invalid argument to option
+* 4 - GID already in use
+
+## Files
+
+* `/etc/group` - new group information (such GID) is appended to this file.
+
+## Examples
+
+```sh
+# groupadd -g 110 contributors
+# groupadd mainteners
+```
+

Userland/Utilities/groupadd.cpp

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+/*
+ * Copyright (c) 2019-2020, Jesse Buhagiar <jooster669@gmail.com>
+ * Copyright (c) 2021, Brandon Pruitt  <brapru@pm.me>
+ * Copyright (c) 2021, Maxime Friess <M4x1me@pm.me>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibCore/ArgsParser.h>
+#include <ctype.h>
+#include <errno.h>
+#include <grp.h>
+#include <string.h>
+#include <unistd.h>
+
+constexpr gid_t GROUPS_GID = 100;
+
+int main(int argc, char** argv)
+{
+    if (pledge("stdio wpath rpath cpath chown", nullptr) < 0) {
+        perror("pledge");
+        return 1;
+    }
+
+    int gid = 0;
+    char const* groupname = nullptr;
+
+    Core::ArgsParser args_parser;
+    args_parser.add_option(gid, "Group ID (gid) for the new group", "gid", 'g', "gid");
+    args_parser.add_positional_argument(groupname, "Name of the group (groupname)", "group");
+
+    args_parser.parse(argc, argv);
+
+    // Let's run a quick sanity check on groupname
+    if (strpbrk(groupname, "\\/!@#$%^&*()~+=`:\n")) {
+        warnln("invalid character in groupname, {}", groupname);
+        return 1;
+    }
+
+    // Disallow names starting with _ and -
+    if (groupname[0] == '_' || groupname[0] == '-' || !isalpha(groupname[0])) {
+        warnln("invalid groupname, {}", groupname);
+        return 1;
+    }
+
+    if (getgrnam(groupname)) {
+        warnln("Group {} already exists!", groupname);
+        return 1;
+    }
+
+    if (gid < 0) {
+        warnln("invalid gid {}!", gid);
+        return 3;
+    }
+
+    // First, let's sort out the gid for the group
+    if (gid > 0) {
+        if (getgrgid(static_cast<uid_t>(gid))) {
+            warnln("gid {} already exists!", gid);
+            return 4;
+        }
+    } else {
+        for (gid = GROUPS_GID; getgrgid(static_cast<uid_t>(gid)); gid++) {
+        }
+    }
+
+    if (gid < 0) {
+        warnln("invalid gid {}", gid);
+        return 3;
+    }
+
+    FILE* grfile = fopen("/etc/group", "a");
+    if (!grfile) {
+        perror("failed to open /etc/group");
+        return 1;
+    }
+
+    struct group g;
+    g.gr_name = const_cast<char*>(groupname);
+    g.gr_passwd = const_cast<char*>("x");
+    g.gr_gid = static_cast<gid_t>(gid);
+    g.gr_mem = nullptr;
+
+    if (putgrent(&g, grfile) < 0) {
+        perror("putpwent");
+        return 1;
+    }
+
+    fclose(grfile);
+
+    return 0;
+}