endgrent man page

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.

endgrent, getgrent, setgrent — group database entry functions

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. When first called, getgrent() shall return a pointer to a group structure containing the first entry in the group 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 to allow repeated searches.

The endgrent() function may be called to close the group database when processing is complete.

These functions need not be thread-safe.

Return Value

When first called, getgrent() shall return a pointer to the first group structure in the group database. Upon subsequent calls it shall return the next group structure in the group database. The getgrent() function shall return a null pointer on end-of-file or an error and errno may 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().

Errors

The getgrent() function may fail if:

EINTR
A signal was caught during the operation.
EIO
An I/O error has occurred.
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.

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.

See Also

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

The Base Definitions volume of POSIX.1‐2008, <grp.h>

Info

2013 IEEE/The Open Group POSIX Programmer's Manual