getgrent(3) — Linux manual page


GETGRENT(3)               Linux Programmer's Manual              GETGRENT(3)

NAME         top

       getgrent, setgrent, endgrent - get group file entry

SYNOPSIS         top

       #include <sys/types.h>
       #include <grp.h>

       struct group *getgrent(void);

       void setgrent(void);

       void endgrent(void);

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

           _XOPEN_SOURCE >= 500
               || /* Glibc since 2.19: */ _DEFAULT_SOURCE
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
       getgrent(), endgrent():
           Since glibc 2.22:
               _XOPEN_SOURCE >= 500 ||
           Glibc 2.21 and earlier
               _XOPEN_SOURCE >= 500
                   || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
                   || /* Glibc versions <= 2.19: */ _BSD_SOURCE ||

DESCRIPTION         top

       The getgrent() function returns a pointer to a structure containing
       the broken-out fields of a record in the group database (e.g., the
       local group file /etc/group, NIS, and LDAP).  The first time
       getgrent() is called, it returns the first entry; thereafter, it
       returns successive entries.

       The setgrent() function rewinds to the beginning of the group
       database, to allow repeated scans.

       The endgrent() function is used to close the group database after all
       processing has been performed.

       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

RETURN VALUE         top

       The getgrent() function returns a pointer to a group structure, or
       NULL if there are no more entries or an error occurs.

       Upon error, errno may be set.  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(), getgrgid(3), or getgrnam(3).  (Do
       not pass the returned pointer to free(3).)

ERRORS         top

       EAGAIN The service was temporarily unavailable; try again later.  For
              NSS backends in glibc this indicates a temporary error talking
              to the backend.  The error may correct itself, retrying later
              is suggested.

       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.

       ENOENT A necessary input file cannot be found.  For NSS backends in
              glibc this indicates the backend is not correctly configured.

       ENOMEM Insufficient memory to allocate group structure.

       ERANGE Insufficient buffer space supplied.

FILES         top

              local group database file

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface   Attribute     Value                       │
       │getgrent()  │ Thread safety │ MT-Unsafe race:grent        │
       │            │               │ race:grentbuf locale        │
       │setgrent(), │ Thread safety │ MT-Unsafe race:grent locale │
       │endgrent()  │               │                             │
       In the above table, grent in race:grent signifies that if any of the
       functions setgrent(), getgrent(), or endgrent() are used in parallel
       in different threads of a program, then data races could occur.

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.

SEE ALSO         top

       fgetgrent(3), getgrent_r(3), getgrgid(3), getgrnam(3),
       getgrouplist(3), putgrent(3), group(5)

COLOPHON         top

       This page is part of release 5.09 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

                                 2017-09-15                      GETGRENT(3)

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