Manual Reference Pages  - GETGRNAM (3)


getgrnam, getgrnam_r, getgrgid, getgrgid_r - get group file entry




#include <sys/types.h> 

#include <grp.h> 

struct group *getgrnam(const char *name);

struct group *getgrgid(gid_t gid);

int getgrnam_r(const char *name, struct group *grp,
char *buf, size_t buflen, struct group **result);

int getgrgid_r(gid_t gid, struct group *grp,
char *buf, size_t buflen, struct group **result);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

getgrnam_r(), getgrgid_r():



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;        /* 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 buflen. 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


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 appropriately. 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.
EIO I/O error.
EMFILE The maximum number (OPEN_MAX) of files was open already in the calling process.
ENFILE The maximum number of files was open already in the system.
ENOMEM Insufficient memory to allocate group structure.
ERANGE Insufficient buffer space supplied.


  local group database file


SVr4, 4.3BSD, POSIX.1-2001.


The formulation given above under "RETURN VALUE" is from POSIX.1-2001. 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 shows that lots of different values occur in this situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM and probably others.


endgrent(3), fgetgrent(3), getgrent(3), getpwnam(3), setgrent(3), group(5)


This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at

GETGRNAM (3) 2012-04-23
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