usr/src/lib/libc/gen/getgrent.3

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.\"     @(#)getgrent.3  6.4 (Berkeley) %G%
.\"
.TH GETGRENT 3  ""
.AT 3
.SH NAME
getgrent, getgrnam, getgrgid, setgroupent, setgrfile, setgrent,
endgrent \- get group file entry
.SH SYNOPSIS
.nf
.B #include <grp.h>
.PP
.B struct group *getgrent()
.PP
.B struct group *getgrnam(name)
.B char *name;
.PP
.B struct group *getgrgid(gid)
.B gid_t gid;
.PP
.B setgroupent(stayopen)
.B int stayopen;
.PP
.B void setgrfile(name)
.B char *name;
.PP
.B setgrent()
.PP
.B void endgrent()
.fi
.SH DESCRIPTION
.I Getgrent,
.I getgrgid
and
.I getgrnam
each return a pointer to a structure containing the broken-out fields
of a line in the group file.  This structure is defined by the include
file
.IR < grp.h >,
and contains the following fields:
.PP
.RS
.nf
struct group {
        char            *gr_name;               /* group name */
        char            *gr_passwd;     /* group password */
        gid_t   gr_gid;         /* group id */
        char            **gr_mem;               /* group members */
};
.ft R
.ad
.fi
.RE
.PP
These fields are more completely described in
.IR group (5).
.PP
.I Getgrnam
and
.I getgrgid
search the group database for a matching group name or group id,
respectively, returning the first one encountered.  Identical group
names or group gids may result in undefined behavior.
.PP
.I Getgrent
sequentially reads the group database and is intended for programs
that wish to step through the complete list of groups.
.PP
All three routines will open the group file for reading, if necesssary.
.PP
.I Setgrfile
changes the default group file to
.IR file ,
thus allowing the use of alternate group files.
.PP
.I Setgroupent
opens the file, or rewinds it if it is already open.  If
.I stayopen
is non-zero, file descriptors are left open, significantly speeding
up subsequent calls.  This functionality is unnecessary for
.I getgrent
as it doesn't close its file descriptors by default.  It should also
be noted that it is dangerous for long-running programs to use this
functionality as the group file may be updated.
.PP
.I Setgrent
is identical to
.I setgroupent
with an argument of zero.
.PP
.I Endgrent
closes any open files.
.PP
.PP
.SH FILES
/etc/group
.SH "SEE ALSO"
 getpwent(3), group(5)
.SH DIAGNOSTICS
The routines
.IR getgrent ,
.IR getgrnam ,
and
.IR getgrgid ,
return a null pointer on EOF or error.
.I Setgroupent
and
.I setgrent
return 0 on failure, 1 on success.
.I Endgrent
and
.I setgrfile
have no return value.
.SH BUGS
All information is contained in a static buffer which is overwritten
by each new call.  It must be copied elsewhere to be retained.
.PP
The routines
.IR getgrent ,
.IR endgrent ,
.IR setgroupent ,
and
.IR setgrent
are fairly useless in a networked environment and should be
avoided, if possible.