endgrent, getgrent, setgrent - group management

Syntax	#include <grp.h> void endgrent (void); void setgrent (void); struct group *getgrent (void);
Description	getgrent() returns a pointer to an object with the structure shown below, which contains the individual fields of a line of the /etc/group file. Each line contains an object of the group structure, which is declared in the header file grp.h, with the following elements: struct group { char *gr_name; /* Name of the group */ char *gr_passwd; /* Encoded group password */ gid_t gr_gid; /* Numerical group ID */ char **gr_mem; /* Pointer to names of the group members*/ }; getgrent() returns a pointer to the first group structure in the file the first time it is called; after this it returns a pointer to the next group structure in the file. In this way, consecutive calls can be used to search through the entire file. setgrent() resets the file position indicator to the beginning of the group file, thus making a repeat search possible. endgrent() can be called at the end of processing in order to close the group file. endgrent(), getgrent() and setgrent() are not thread-safe.
Return val.	getgrent(): Pointer to the first group structure of the group file at the first call Pointer to the next group structure of the group file
		at subsequent calls
	Null pointer	at EOF or if an error occurs. errno is set to indicate the error.
Errors	getgrent() will fail if:
	EINTR EIO EMFILE ENFILE	getgrent() was interrupted by a signal. an I/O error occurred during reading or writing. The calling process contains {OPEN_MAX} open file descriptors. The maximum permissible number of files is open in the system.
	Extension
	ENOMEM	There is not enough memory for storing the global data of getgrent(). (End)
Notes	The return value of getgrent() can point to an area that will be overwritten by a subsequent call of getgrgid(), getgrnam() or getgrent(). These functions continue to be offered because they were common in the past. However, the format of the group structure depends on the implementation, which is why applications that use these functions are not portable. Portable applications should therefore use getgrnam() and getgrgid().
See also	getgrgid(), getgrnam(), getlogin(), getpwent(), grp.h.