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new 9704481224a libc/unistd: add getgroups()
9704481224a is described below
commit 9704481224a199506bfb74702c2b3638081d8474
Author: Xiang Xiao <[email protected]>
AuthorDate: Sun Jun 21 01:48:17 2026 +0800
libc/unistd: add getgroups()
Add getgroups() to the C library. NuttX has no supplementary group
IDs, so it reports a single group, the effective group ID, and follows
POSIX for the gidsetsize == 0 and short-buffer (EINVAL) cases.
Signed-off-by: Xiang Xiao <[email protected]>
---
Documentation/standards/posix.rst | 2 +-
include/unistd.h | 2 +
libs/libc/unistd/CMakeLists.txt | 1 +
libs/libc/unistd/Make.defs | 2 +-
libs/libc/unistd/lib_getgroups.c | 85 +++++++++++++++++++++++++++++++++++++++
5 files changed, 90 insertions(+), 2 deletions(-)
diff --git a/Documentation/standards/posix.rst
b/Documentation/standards/posix.rst
index 577abf16ce5..cdca6eb748e 100644
--- a/Documentation/standards/posix.rst
+++ b/Documentation/standards/posix.rst
@@ -1972,7 +1972,7 @@ User and Group:
+--------------------------------+---------+
| :c:func:`getgid` | Yes |
+--------------------------------+---------+
-| getgroups() | No |
+| :c:func:`getgroups` | Yes |
+--------------------------------+---------+
| getlogin() | No |
+--------------------------------+---------+
diff --git a/include/unistd.h b/include/unistd.h
index 6c7f7d1bcf3..63ded5444ac 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -494,6 +494,8 @@ gid_t getegid(void);
int setreuid(uid_t ruid, uid_t euid);
int setregid(gid_t rgid, gid_t egid);
+int getgroups(int, gid_t[]);
+
int getentropy(FAR void *buffer, size_t length);
void sync(void);
diff --git a/libs/libc/unistd/CMakeLists.txt b/libs/libc/unistd/CMakeLists.txt
index 797ff8aba9e..eb4ca8e5e93 100644
--- a/libs/libc/unistd/CMakeLists.txt
+++ b/libs/libc/unistd/CMakeLists.txt
@@ -65,6 +65,7 @@ set(SRCS
lib_getpgrp.c
lib_getpgid.c
lib_getsid.c
+ lib_getgroups.c
lib_setpgid.c
lib_setsid.c
lib_lockf.c
diff --git a/libs/libc/unistd/Make.defs b/libs/libc/unistd/Make.defs
index e7852230ad7..e3e5ed3a214 100644
--- a/libs/libc/unistd/Make.defs
+++ b/libs/libc/unistd/Make.defs
@@ -32,7 +32,7 @@ CSRCS += lib_setrlimit.c lib_getrlimit.c lib_setpriority.c
lib_getpriority.c
CSRCS += lib_futimes.c lib_lutimes.c lib_gethostname.c lib_sethostname.c
CSRCS += lib_fchownat.c lib_linkat.c lib_readlinkat.c lib_symlinkat.c
CSRCS += lib_unlinkat.c lib_usleep.c lib_getpgrp.c lib_getpgid.c
-CSRCS += lib_getsid.c lib_setpgid.c lib_setsid.c
+CSRCS += lib_getsid.c lib_getgroups.c lib_setpgid.c lib_setsid.c
CSRCS += lib_lockf.c lib_flock.c lib_getpass.c
CSRCS += lib_chdir.c lib_fchdir.c lib_confstr.c lib_ulimit.c
diff --git a/libs/libc/unistd/lib_getgroups.c b/libs/libc/unistd/lib_getgroups.c
new file mode 100644
index 00000000000..53cbc11ba82
--- /dev/null
+++ b/libs/libc/unistd/lib_getgroups.c
@@ -0,0 +1,85 @@
+/****************************************************************************
+ * libs/libc/unistd/lib_getgroups.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership. The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <unistd.h>
+#include <errno.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: getgroups
+ *
+ * Description:
+ * The getgroups() function returns the supplementary group IDs of the
+ * calling process in the array grouplist. NuttX does not support
+ * supplementary group IDs, so the calling process is treated as belonging
+ * to a single group: its effective group ID.
+ *
+ * Input Parameters:
+ * gidsetsize - The number of elements available in grouplist.
+ * grouplist - The buffer used to return the group IDs.
+ *
+ * Returned Value:
+ * On success, the number of group IDs is returned. If gidsetsize is zero,
+ * the total number of group IDs is returned without modifying grouplist.
+ * On failure, -1 is returned and errno is set appropriately.
+ *
+ ****************************************************************************/
+
+int getgroups(int gidsetsize, gid_t grouplist[])
+{
+ if (gidsetsize < 0)
+ {
+ set_errno(EINVAL);
+ return -1;
+ }
+
+ /* If gidsetsize is zero, return the number of group IDs without touching
+ * grouplist.
+ */
+
+ if (gidsetsize == 0)
+ {
+ return 1;
+ }
+
+ if (grouplist == NULL)
+ {
+ set_errno(EFAULT);
+ return -1;
+ }
+
+ /* NuttX has no notion of supplementary group IDs. Report the single
+ * effective group ID of the calling process.
+ */
+
+ grouplist[0] = getegid();
+ return 1;
+}
