struct group *getgrent(void);
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 reentrant. A function that is not required to be reentrant is not required to be thread-safe.
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 return value may point to a static area which is overwritten by a subsequent call to getgrgid(), getgrnam(), or getgrent().
The getgrent() function may fail if:
The following sections are informative.
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.
getgrgid() , getgrnam() , getlogin() , getpwent() , the Base Definitions volume of IEEE Std 1003.1-2001, <grp.h>