Linux manual pages Section 3: Subroutines  

Name

getgrent, setgrent, endgrent — get group file entry

Synopsis

#include <sys/types.h>
#include <grp.h>
struct group *getgrent( void);  
 
void setgrent( void);  
 
void endgrent( void);  
 
[Note] Note
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
setgrent():
_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED ||
/* Since glibc 2.12:
*/ _POSIX_C_SOURCE >= 200809L
getgrent(), endgrent():
_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

DESCRIPTION

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;
/* group members */
};

For more information about the fields of this structure, see group(5).

RETURN VALUE

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

EINTR

A signal was caught.

EIO

I/O error.

EMFILE

The calling process already has too many open files.

ENFILE

Too many open files in the system.

ENOMEM

Insufficient memory to allocate group structure.

ERANGE

Insufficient buffer space supplied.

FILES

/etc/group

local group database file

ATTRIBUTES

Multithreading (see pthreads(7))

The getgrent() function is not thread-safe.

The setgrent() and endgrent() functions are thread-safe.

CONFORMING TO

SVr4, 4.3BSD, POSIX.1-2001.

SEE ALSO

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

COLOPHON

This page is part of release 3.52 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man−pages/.


  Copyright 1993 David Metcalfe (davidprism.demon.co.uk)

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References consulted:
    Linux libc source code
    Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
    386BSD man pages
Modified Sat Jul 24 19:29:54 1993 by Rik Faith (faithcs.unc.edu)