endgrent - Man Page

group database entry functions

Prolog

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

Synopsis

#include <grp.h>

void endgrent(void);
struct group *getgrent(void);
void setgrent(void);

Description

The getgrent() function shall return a pointer to a structure containing the broken-out fields of an entry in the group database. If the group database is not already open, getgrent() shall open it and return a pointer to a group structure containing the first entry in the database. Thereafter, it shall return a pointer to a group structure containing the next group structure in the group database, so successive calls may be used to search the entire database.

An implementation that provides extended security controls may impose further implementation-defined restrictions on accessing the group database. In particular, the system may deny the existence of some or all of the group database entries associated with groups other than those groups associated with the caller and may omit users other than the caller from the list of members of groups in database entries that are returned.

The setgrent() function shall rewind the group database so that the next getgrent() call returns the first entry, allowing repeated searches.

The endgrent() function shall close the group database.

The setgrent() and endgrent() functions shall not change the setting of errno if successful.

On error, the setgrent() and endgrent() functions shall set errno to indicate the error.

Since no value is returned by the setgrent() and endgrent() functions, an application wishing to check for error situations should set errno to 0, then call the function, then check errno.

These functions need not be thread-safe.

Return Value

On successful completion, getgrent() shall return a pointer to a group structure. On end-of-file, getgrent() shall return a null pointer and shall not change the setting of errno. On error, getgrent() shall return a null pointer and errno shall be set to indicate the error.

The application shall not modify the structure to which the return value points, nor any storage areas pointed to by pointers within the structure. The returned pointer, and pointers within the structure, might be invalidated or the structure or the storage areas might be overwritten by a subsequent call to getgrgid(), getgrnam(), or getgrent(). The returned pointer, and pointers within the structure, might also be invalidated if the calling thread is terminated.

Errors

These functions may fail if:

EINTR

A signal was caught during the operation.

EIO

An I/O error has occurred.

In addition, the getgrent() and setgrent() functions may fail if:

EMFILE

All file descriptors available to the process are currently open.

ENFILE

The maximum allowable number of files is currently open in the system.

The following sections are informative.

Examples

None.

Application Usage

These functions are provided due to their historical usage. Applications should avoid dependencies on fields in the group database, whether the database is a single file, or where in the file system name space the database resides. Applications should use getgrnam() and getgrgid() whenever possible because it avoids these dependencies.

Rationale

None.

Future Directions

None.

See Also

endpwent(), getgrgid(), getgrnam(), getlogin()

The Base Definitions volume of POSIX.1-2017, <grp.h>

Referenced By

endpwent(3p), getgrgid(3p), getgrnam(3p), grp.h(0p).

2017 IEEE/The Open Group POSIX Programmer's Manual