Content-type: text/html Man page of getgrent

getgrent

Section: C Library Functions (3)
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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.so, libc.a)  

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);

[Digital]  The following obsolete functions are supported in order to maintain backward compatibility with previous versions of the operating system. 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:

getgrgid_r, getgrnam_r:  POSIX.1c

getgrgid, getgrnam:  XPG4, XPG4-UNIX

endgrent, getgrent, setgrent:  XPG4-UNIX

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, fgetgrent, 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 getgrent_r function, so that subsequent calls will return subsequent entries from the /etc/group file.

[POSIX]  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.

[POSIX] 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 containing a matching entry. Upon failure, these functions return NULL.

[POSIX]  The getgrgid_r and getgrnam_r functions return a value of 0 (zero) on success and an error number on failure.

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: [POSIX]  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


 

Index

NAME
LIBRARY
SYNOPSIS
STANDARDS
PARAMETERS
DESCRIPTION
NOTES
RETURN VALUES
ERRORS
RELATED INFORMATION

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Time: 02:41:29 GMT, October 02, 2010