INITGROUPS(3) Linux Programmer's Manual INITGROUPS(3)NAME
initgroups - initialize the supplementary group access list
SYNOPSIS
#include <sys/types.h>
#include <grp.h>
int initgroups(const char *user, gid_t group);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
initgroups():
Since glibc 2.19:
_DEFAULT_SOURCE
Glibc 2.19 and earlier:
_BSD_SOURCE
DESCRIPTION
The initgroups() function initializes the group access list by reading the group database /etc/group and using all groups of which user is
a member. The additional group group is also added to the list.
The user argument must be non-NULL.
RETURN VALUE
The initgroups() function returns 0 on success. On error, -1 is returned, and errno is set appropriately.
ERRORS
ENOMEM Insufficient memory to allocate group information structure.
EPERM The calling process has insufficient privilege. See the underlying system call setgroups(2).
FILES
/etc/group
group database file
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
+-------------+---------------+----------------+
|Interface | Attribute | Value |
+-------------+---------------+----------------+
|initgroups() | Thread safety | MT-Safe locale |
+-------------+---------------+----------------+
CONFORMING TO
SVr4, 4.3BSD.
SEE ALSO getgroups(2), setgroups(2), credentials(7)COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the
latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
GNU 2017-09-15 INITGROUPS(3)
Check Out this Related Man Page
GETGROUPS(2) Linux Programmer's Manual GETGROUPS(2)NAME
getgroups, setgroups - get/set list of supplementary group IDs
SYNOPSIS
#include <sys/types.h>
#include <unistd.h>
int getgroups(int size, gid_t list[]);
#include <grp.h>
int setgroups(size_t size, const gid_t *list);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
setgroups(): _BSD_SOURCE
DESCRIPTION
getgroups() returns the supplementary group IDs of the calling process in list. The argument size should be set to the maximum number of
items that can be stored in the buffer pointed to by list. If the calling process is a member of more than size supplementary groups, then
an error results. It is unspecified whether the effective group ID of the calling process is included in the returned list. (Thus, an
application should also call getegid(2) and add or remove the resulting value.)
If size is zero, list is not modified, but the total number of supplementary group IDs for the process is returned. This allows the caller
to determine the size of a dynamically allocated list to be used in a further call to getgroups().
setgroups() sets the supplementary group IDs for the calling process. Appropriate privileges (Linux: the CAP_SETGID capability) are
required. The size argument specifies the number of supplementary group IDs in the buffer pointed to by list.
RETURN VALUE
On success, getgroups() returns the number of supplementary group IDs. On error, -1 is returned, and errno is set appropriately.
On success, setgroups() returns 0. On error, -1 is returned, and errno is set appropriately.
ERRORS
EFAULT list has an invalid address.
getgroups() can additionally fail with the following error:
EINVAL size is less than the number of supplementary group IDs, but is not zero.
setgroups() can additionally fail with the following errors:
EINVAL size is greater than NGROUPS_MAX (32 before Linux 2.6.4; 65536 since Linux 2.6.4).
ENOMEM Out of memory.
EPERM The calling process has insufficient privilege.
CONFORMING TO
SVr4, 4.3BSD. The getgroups() function is in POSIX.1-2001. Since setgroups() requires privilege, it is not covered by POSIX.1-2001.
NOTES
A process can have up to NGROUPS_MAX supplementary group IDs in addition to the effective group ID. The set of supplementary group IDs is
inherited from the parent process, and preserved across an execve(2).
The maximum number of supplementary group IDs can be found using sysconf(3):
long ngroups_max;
ngroups_max = sysconf(_SC_NGROUPS_MAX);
The maximum return value of getgroups() cannot be larger than one more than this value.
SEE ALSO getgid(2), setgid(2), getgrouplist(3), initgroups(3), capabilities(7), credentials(7)COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2008-06-03 GETGROUPS(2)