This section explains how a program can read the list of all groups in
the system, one group at a time. The functions described here are
declared in grp.h.
You can use the fgetgrent function to read group entries from a
particular file.
— Function: struct group * fgetgrent (FILE *stream)
The fgetgrent function reads the next entry from stream.
It returns a pointer to the entry. The structure is statically
allocated and is overwritten on subsequent calls to fgetgrent. You
must copy the contents of the structure if you wish to save the
information.
The stream must correspond to a file in the same format as the standard
group database file.
— Function: int fgetgrent_r (FILE *stream, struct group *result_buf, char *buffer, size_t buflen, struct group **result)
This function is similar to fgetgrent in that it reads the next
user entry from stream. But the result is returned in the
structure pointed to by result_buf. The first buflen bytes
of the additional buffer pointed to by buffer are used to contain
additional information, normally strings which are pointed to by the
elements of the result structure.
This stream must correspond to a file in the same format as the standard
group database file.
If the function returns zero result points to the structure with
the wanted data (normally this is in result_buf). If errors
occurred the return value is non-zero and result contains a null
pointer.
The way to scan all the entries in the group database is with
setgrent, getgrent, and endgrent.
— Function: void setgrent (void)
This function initializes a stream for reading from the group data base.
You use this stream by calling getgrent or getgrent_r.
— Function: struct group * getgrent (void)
The getgrent function reads the next entry from the stream
initialized by setgrent. It returns a pointer to the entry. The
structure is statically allocated and is overwritten on subsequent calls
to getgrent. You must copy the contents of the structure if you
wish to save the information.
— Function: int getgrent_r (struct group *result_buf, char *buffer, size_t buflen, struct group **result)
This function is similar to getgrent in that it returns the next
entry from the stream initialized by setgrent. Like
fgetgrent_r, it places the result in user-supplied buffers
pointed to result_buf and buffer.
If the function returns zero result contains a pointer to the data
(normally equal to result_buf). If errors occurred the return
value is non-zero and result contains a null pointer.
— Function: void endgrent (void)
This function closes the internal stream used by getgrent or
getgrent_r.
Published under the terms of the GNU General Public License
