NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | FILES | ATTRIBUTES | VERSIONS | STANDARDS | HISTORY | SEE ALSO | COLOPHON
getgrnam(3) Library Functions Manual getgrnam(3)
getgrnam, getgrnam_r, getgrgid, getgrgid_r - get group file entry
Standard C library (libc, -lc)
#include <sys/types.h> #include <grp.h> struct group *getgrnam(const char *name); struct group *getgrgid(gid_t gid); int getgrnam_r(const char *restrict name, struct group *restrict grp, char buf[restrict .size], size_t size, struct group **restrict result); int getgrgid_r(gid_t gid, struct group *restrict grp, char buf[restrict .size], size_t size, struct group **restrict result); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): getgrnam_r(), getgrgid_r(): _POSIX_C_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
The getgrnam() function returns a pointer to a structure
containing the broken-out fields of the record in the group
database (e.g., the local group file /etc/group, NIS, and LDAP)
that matches the group name name.
The getgrgid() function returns a pointer to a structure
containing the broken-out fields of the record in the group
database that matches the group ID gid.
The group structure is defined in <grp.h> as follows:
struct group {
char *gr_name; /* group name */
char *gr_passwd; /* group password */
gid_t gr_gid; /* group ID */
char **gr_mem; /* NULL-terminated array of pointers
to names of group members */
};
For more information about the fields of this structure, see
group(5).
The getgrnam_r() and getgrgid_r() functions obtain the same
information as getgrnam() and getgrgid(), but store the retrieved
group structure in the space pointed to by grp. The string fields
pointed to by the members of the group structure are stored in the
buffer buf of size size. A pointer to the result (in case of
success) or NULL (in case no entry was found or an error occurred)
is stored in *result.
The call
sysconf(_SC_GETGR_R_SIZE_MAX)
returns either -1, without changing errno , or an initial suggested
size for buf. (If this size is too small, the call fails with
ERANGE, in which case the caller can retry with a larger buffer.)
The getgrnam() and getgrgid() functions return a pointer to a group structure, or NULL if the matching entry is not found or an error occurs. If an error occurs, errno is set to indicate the error. If one wants to check errno after the call, it should be set to zero before the call. The return value may point to a static area, and may be overwritten by subsequent calls to getgrent(3), getgrgid(), or getgrnam(). (Do not pass the returned pointer to free(3).) On success, getgrnam_r() and getgrgid_r() return zero, and set *result to grp. If no matching group record was found, these functions return 0 and store NULL in *result. In case of error, an error number is returned, and NULL is stored in *result.
0 or ENOENT or ESRCH or EBADF or EPERM or ... The given name or gid was not found. EINTR A signal was caught; see signal(7). EIO I/O error. EMFILE The per-process limit on the number of open file descriptors has been reached. ENFILE The system-wide limit on the total number of open files has been reached. ENOMEM Insufficient memory to allocate group structure. ERANGE Insufficient buffer space supplied.
/etc/group local group database file
For an explanation of the terms used in this section, see attributes(7). ┌───────────────┬───────────────┬────────────────────────────────┐ │ Interface │ Attribute │ Value │ ├───────────────┼───────────────┼────────────────────────────────┤ │ getgrnam() │ Thread safety │ MT-Unsafe race:grnam locale │ ├───────────────┼───────────────┼────────────────────────────────┤ │ getgrgid() │ Thread safety │ MT-Unsafe race:grgid locale │ ├───────────────┼───────────────┼────────────────────────────────┤ │ getgrnam_r(), │ Thread safety │ MT-Safe locale │ │ getgrgid_r() │ │ │ └───────────────┴───────────────┴────────────────────────────────┘
The formulation given above under "RETURN VALUE" is from POSIX.1. It does not call "not found" an error, hence does not specify what value errno might have in this situation. But that makes it impossible to recognize errors. One might argue that according to POSIX errno should be left unchanged if an entry is not found. Experiments on various UNIX-like systems show that lots of different values occur in this situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM, and probably others.
POSIX.1-2008.
POSIX.1-2001, SVr4, 4.3BSD.
endgrent(3), fgetgrent(3), getgrent(3), getpwnam(3), setgrent(3), group(5)
This page is part of the man-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.10.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025年02月02日. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org Linux man-pages 6.10 2024年12月24日 getgrnam(3)
Pages that refer to this page: getent(1), fgetgrent(3), getgrent(3), getgrent_r(3), getpwnam(3), getspnam(3), id_t(3type), group(5), nscd(8)
HTML rendering created 2025年02月02日 by Michael Kerrisk, author of The Linux Programming Interface.
For details of in-depth Linux/UNIX system programming training courses that I teach, look here.
Hosting by jambit GmbH.
Cover of TLPI