getgrent(3) Library Functions Manual getgrent(3)
NAME
endgrent, fgetgrent, getgrent, getgrgid, getgrnam, setgrent, endgrent_r, fgetgrent_r, getgrent_r, getgrgid_r, getgrnam_r, setgrent_r -
Access group information in the user database
LIBRARY
Standard C Library (libc)
SYNOPSIS
#include <grp.h>
void endgrent(void);
struct group *fgetgrent(
FILE *f);
struct group *getgrent(void);
struct group *getgrgid(
gid_t gid);
struct group *getgrnam(
const char *name);
void setgrent(void);
void endgrent_r(
FILE **gr_fp);
int fgetgrent_r(
FILE *f,
struct group *grp,
char *buffer,
int len);
int getgrent_r(
struct group *grp,
char *buffer,
int len,
FILE **gr_fp);
int getgrgid_r(
gid_t gid,
struct group *grp,
char *buffer,
size_t len,
struct group **result);
int getgrnam_r(
const char *name,
struct group *grp,
char *buffer,
size_t len,
struct group **result);
int setgrent_r(
FILE **gr_fp);
The following obsolete functions do not conform to industry standards and are supported only for backward compatibility. You should not
use them in new designs.
int getgrgid_r(
gid_t gid,
struct group *grp,
char *buffer,
int len);
int getgrnam_r(
const char *name,
struct group *grp,
char *buffer,
int len);
int setgrent(void);
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
endgrent, getgrent, getgrgid, getgrgid_r, getgrnam, getgrnam_r, setgrent: XSH5.0
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
Specifies the name of the group for which the group file entry is to be retrieved. Specifies the group ID of the group for which the group
file entry is to be retrieved. Provides storage to hold the retrieved group structure. Specifies the working buffer that is able to hold
the longest group entry in the database (/etc/group). Specifies the length of buffer. This length should be sufficient for buf to hold
the longest /etc/group line. Upon successful return, points to the retrieved group structure. Upon unsuccessful return, the result is set
to NULL. Specifies a file that contains the next group structure (initialized by the user). Specifies a file that contains the next group
structure (initialized by the user). This file should have the same format as /etc/group. The minimum buffer size is 1024 bytes as defined
for SIABUFSIZ in /usr/include/sia.h. Specifies the length of buffer. The minimum buffer size is 1024 bytes as defined for SIABUFSIZ in
/usr/include/sia.h.
DESCRIPTION
The getgrent, getgrgid, getgrnam, setgrent, endgrent, and fgetgrent functions may be used to access the basic group attributes.
The setgrent function opens the user database (if not already open) and rewinds to the first group entry in the database.
The getgrent, getgrnam, and getgrgid functions return information about the requested group. The getgrent function returns the next group
in the sequential search. The getgrnam function returns the first group in the database with the gr_name field that matches the name
parameter. The getgrgid function returns the first group in the database with a gr_gid field that matches the gid parameter. The endgrent
function closes the user database.
The group structure, which is returned by the getgrent, getgrgid, and getgrnam functions, is defined in the grp.h header file, and contains
the following members: The name of the group. The password of the group. (Note that this field is not used by the system, so its value is
meaningless.) The ID of the group. The members of the group.
The fgetgrent function gets a group file entry from the file specified by the f parameter, rather than assuming that it comes from the
/etc/group file. This file must have the format of the /etc/group file.
The endgrent_r, fgetgrent_r, getgrent_r, getgrgid_r, getgrnam_r, and setgrent_r, functions are the reentrant versions of endgrent, fget-
grent, getgrent, getgrgid, getgrnam, and setgrent, respectively.
The endgrent_r, fgetgrent_r, getgrent_r, and setgrent_r, functions use the f and gr_fp parameters to keep track of the calls to the get-
grent_r function, so that subsequent calls will return subsequent entries from the /etc/group file.
Upon successful completion, the fgetgrent_r, getgrent_r, getgrgid_r, and getgrnam_r functions store their results in the buffer pointed to
by the grp parameter, with references to the working buffer. The pointer to the grp is also stored in result.
NOTES
The data that is returned by the fgetgrent, getgrent, getgrgid, and getgrnam functions is stored in a static area and will be overwritten
on subsequent calls to these routines.
The fgetgrent, getgrent, getgrnam, and getgrgid functions are not supported for multithreaded applications. Instead, their reentrant
equivalents, fgetgrent_r, getgrent_r, getgrnam_r, and getgrgid_r, should be used with multiple threads.
Note that the caller is expected to initialize *gr_fp to NULL before using it for the first time.
Note also that entries which are excessively long will be ignored by both the reentrant and non-reentrant functions.
RETURN VALUES
Upon successful completion, the fgetgrent, getgrent, getgrgid, and getgrnam functions return a pointer to a valid group structure contain-
ing a matching entry. Upon failure, these functions return NULL.
The getgrgid_r and getgrnam_r functions return a value of 0 (zero) on success. If the user or group is not found in the password or group
database, these routines return 0 for the status and a NULL in the returned "result" pointer.
The fgetgrent_r and getgrent_r functions, as well as the obsolete versions of the getgrgid_r and getgrnam_r functions, return a value of 0
(zero) for success and a value of -1 for failure.
The backward-compatible version of the setgrent function returns a value of 1 for success and a value of 0 (zero) for failure.
The setgrent_r function returns a value of 0 (zero) for success and a value of -1 for failure.
ERRORS
If any of the following conditions occurs, the getgrgid_r and getgrnam_r functions set errno to the corresponding value: The amount of
storage specified by buffer and len is too small to contain the data to be referenced by the resulting struct group structure.
RELATED INFORMATION
Functions: getpwent(3)
Standards: standards(5) delim off
getgrent(3)