136 lines
3.1 KiB
Groff
136 lines
3.1 KiB
Groff
.TH GETGRENT 3
|
|
.SH NAME
|
|
getgrent, getgrnam, getgrgid, setgrent, endgrent, setgrfile \- group file routines
|
|
.SH SYNOPSIS
|
|
.ft B
|
|
.nf
|
|
#include <grp.h>
|
|
|
|
struct group *getgrent(void)
|
|
struct group *getgrnam(const char *\fIname\fP)
|
|
struct group *getgrgid(gid_t \fIgid\fP)
|
|
int setgrent(void)
|
|
void endgrent(void)
|
|
void setgrfile(const char *\fIfile\fP)
|
|
.fi
|
|
.ft P
|
|
.SH DESCRIPTION
|
|
These functions are used to obtain information from the group file. They
|
|
return this information in a
|
|
.B struct group
|
|
as defined by <grp.h>:
|
|
.PP
|
|
.nf
|
|
.ta +4n +6n +15n
|
|
struct group {
|
|
char *gr_name; /* login name */
|
|
char *gr_passwd; /* encrypted password */
|
|
gid_t gr_gid; /* numeric group id */
|
|
char **gr_mem; /* null-terminated list of group members */
|
|
};
|
|
.fi
|
|
.PP
|
|
.B Getgrent()
|
|
reads the group file entry by entry.
|
|
.B Getgrnam()
|
|
scans the entire group file for the group with the given
|
|
.IR name .
|
|
.B Getgrgid()
|
|
looks for the first group with the given
|
|
.IR gid .
|
|
The
|
|
.B setgrent()
|
|
and
|
|
.B endgrent()
|
|
functions are used to open and later close the group file. With
|
|
.B setgrfile()
|
|
one can specify the file to read other than the normal group file. This
|
|
only sets the name, the next
|
|
.B setgrent()
|
|
call will open the file. Do not touch the file name while it is active.
|
|
Use
|
|
.B setgrfile(NULL)
|
|
to revert back to the normal group file.
|
|
.PP
|
|
The usual way to scan the group file is (error checking omitted):
|
|
.PP
|
|
.RS
|
|
.nf
|
|
.DT
|
|
setgrent();
|
|
while ((gr = getgrent()) != NULL)
|
|
if (appropriate_test(gr)) break;
|
|
endgrent();
|
|
.fi
|
|
.RE
|
|
.PP
|
|
The
|
|
.B gr
|
|
variable contains the entry that is wanted if non-NULL. The
|
|
.B getgrnam()
|
|
and
|
|
.B getgrgid()
|
|
functions are implemented as in this example, with error checking of course.
|
|
.PP
|
|
.B Getgrent()
|
|
calls
|
|
.B setgrent()
|
|
if this has not yet been done.
|
|
.B Setgrent()
|
|
first calls
|
|
.B endgrent()
|
|
if the group file is still open. (Other implementations may simply
|
|
rewind the file.)
|
|
.SH FILES
|
|
.TP 15
|
|
.B /etc/group
|
|
The group file database.
|
|
.SH "SEE ALSO"
|
|
.BR getgroups (2),
|
|
.BR initgroups (3),
|
|
.BR getpwent (3),
|
|
.BR passwd (5).
|
|
.SH DIAGNOSTICS
|
|
.B Setgrent()
|
|
has the same return value and error codes as the
|
|
.BR open (2)
|
|
call it uses to open the group file. The
|
|
.BI get xxx ()
|
|
functions return NULL on end of file, entry not found, or error. You can
|
|
set
|
|
.B errno
|
|
to zero before the call and check it after.
|
|
.SH NOTES
|
|
All
|
|
.BI get xxx ()
|
|
routines return a pointer to static storage that is overwritten in each call.
|
|
.PP
|
|
Only
|
|
.B getgrnam()
|
|
and
|
|
.B getgrgid()
|
|
are defined by \s-2POSIX\s+2. The
|
|
.B _MINIX_SOURCE
|
|
macro must be defined before including <grp.h> to make the other functions
|
|
visible. The
|
|
.B gr_passwd
|
|
field is also not defined by \s-2POSIX\s+2, but is always visible.
|
|
Portable code cannot reliably detect errors by setting
|
|
.B errno
|
|
to zero. Under Minix it is better to make a
|
|
.B getgrent()
|
|
scan if you need to look up several group-id's or names, but portable code
|
|
had better use several
|
|
.B getgrgid()
|
|
or
|
|
.B getgrnam()
|
|
calls. The
|
|
.B getgrent()
|
|
is usually available on other systems, but may be very expensive. See
|
|
.BR initgroups (3)
|
|
if you are after supplementary group id's.
|
|
.SH AUTHOR
|
|
Kees J. Bot (kjb@cs.vu.nl)
|
|
|
|
.\"
|
|
.\" $PchId: getgrent.3,v 1.2 1996/04/11 06:35:01 philip Exp $
|