Manpages - getgrent.3

getgrent, setgrent, endgrent - get group file entry

  #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)):

*setgrent*():

      _XOPEN_SOURCE >= 500
          || /* Glibc since 2.19: */ _DEFAULT_SOURCE
          || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

*getgrent*(), *endgrent*():

      Since glibc 2.22:
          _XOPEN_SOURCE >= 500 || _DEFAULT_SOURCE
      Glibc 2.21 and earlier
          _XOPEN_SOURCE >= 500
              || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
              || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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 *group*(5).

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).)

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.

/etc/group

local group database file

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

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.

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

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

This page is part of release 5.13 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/.