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You are here: manpages

getgrnam

Section: C Library Functions (3)
Updated: 202-0-08
Index Return to Main Contents

NAME

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

LIBRARY

Standard C library (libc,~-lc)

SYNOPSIS

#include <sys/types.h>
#include <grp.h>
struct group *getgrnam(const char *name);
struct group *getgrgid(gid_t gid);
int getgrnam_r(size_t size;
               const char *restrict name, struct group *restrict grp,
               char buf[restrict size], size_t size,
               struct group **restrict result);
int getgrgid_r(size_t size;
               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

DESCRIPTION

The getgrnam() function returns a pointer to a structure containing the broke-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 broke-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.)

RETURN VALUE

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.

ERRORS

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 pe-process limit on the number of open file descriptors has been reached.
ENFILE: The syste-wide limit on the total number of open files has been reached.
ENOMEM: Insufficient memory to allocate group structure.
ERANGE: Insufficient buffer space supplied.

FILES

/etc/group: local group database file

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
getgrnam()	Thread safety	M-Unsafe race:grnam locale
getgrgid()	Thread safety	M-Unsafe race:grgid locale
getgrnam_r(), getgrgid_r()	Thread safety	M-Safe locale

VERSIONS

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 UNI-like systems show that lots of different values occur in this situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM, and probably others.