roger@nmtvax.UUCP (11/02/85)
# This is a shell archive. Remove anything before this line, then
# unpack it by saving it in a file and typing "sh file". (Files
# unpacked will be owned by you and have default permissions.)
#
# This archive contains:
# README getutmp.c
echo x - README
cat > "README" << '//E*O*F README//'
Contained in the other file (getutmp.c) is a series of routines
that allows someone to access the utmp file on the system in the way
that getpwent(3), getgrent(3), and the like do it. They kinda make
accessing utmp easier to do (no fuss, no muss!). The routines work
well on 4.2 and 2.9 (for as much as I've tried them) ; I don't know
about other UNIX's though. It has a rather bad dependency on <utmp.h>
where they use an 8 in the code. It would seem that it should
be #def'ed, so dependencies like this don't develope. Too late.
In any event, enjoy them. Send fixes or changes back to me if you
like. Do anything you like with them except use them for profit.
One of these days, I may even get some documentation done up for it too.
Roger Levasseur
New Mexico Tech
{ ucbvax | lanl | gatech } !unmvax!nmtvax!roger
//E*O*F README//
echo x - getutmp.c
cat > "getutmp.c" << '//E*O*F getutmp.c//'
/*
# getutmp -- routines to get utmp file entries
# Roger Maurice Levasseur
# July 1985 - 4.2BSD
# October 1985 - 2.9BSD
# New Mexico Tech
#
*/
#include <sys/types.h>
#include <sys/file.h>
#include <utmp.h>
#include <pwd.h>
#ifndef NULL
#define NULL 0
#endif
#define UTMP "/etc/utmp" /* location of the utmp file */
/*
# when utmp is closed, u_utmp contains a -1,
# otherwise it will contain the descriptor
*/
static int u_utmp = -1;
/*
# setutent -- open or rewind the utmp file to the start of the file
#
# A successful open returns a 1 (true) otherwise a NULL.
*/
setutent()
{
if (u_utmp >= 0) {
/*
# it is open already; rewind it
# if the long seek fails, return it as an error
*/
if (lseek(u_utmp,0L,0) == -1) return(NULL);
return(1);
}
/*
# it is not open, so lets open it
# 0 == READ ONLY
*/
if ((u_utmp = open(UTMP,0)) < 0) return(NULL);
else return(1);
}
/*
# endutent -- close the utmp file if it is open.
#
# It is not an error to call this routine if the file is already closed.
# A 1 (true) is returned on successful closure, a NULL on error
*/
endutent()
{
if (u_utmp >= 0) {
if (close(u_utmp) == -1) {
/*
# might be wise just to check anyhow in case funky
# things were done when getutmp wasn't looking.
*/
u_utmp = -1;
return(NULL);
}
u_utmp = -1;
}
return(1);
}
/*
# getutent -- get the next entry in the utmp file.
#
# Returns a pointer to the next valid structure, or returns a
# NULL on error, or an EOF, meaning the utmp file is exhausted.
*/
struct utmp *getutent()
{
static struct utmp next;
if (u_utmp < 0) {
/*
# if the file hasn't been open yet, get it opened
# and handle errors accordingly
*/
if ( setutent() == NULL) return(NULL);
}
for (;;) { /* loop until a valid entry, or file is exhausted */
if (read(u_utmp,&next,sizeof(struct utmp)) == 0) return(NULL);
if (next.ut_name[0] == '\0') continue; /* an 'empty' entry */
return(&next);
}
}
/*
# getutuid -- if a user by the given user id is on the system, this
# returns a pointer to a struct utmp; otherwise a NULL pointer
*/
struct utmp *getutuid(uid)
int uid;
{
struct utmp *up;
struct passwd *getpwnam(), *ptr;
char nambuf[9];
if (setutent() == NULL) return(NULL); /* start from beginning */
while (up = getutent()) {
/*
# assuming here too that 8 is unwise, but it is not
# #def'd in the include file like it should be, so....
*/
strncpy(nambuf,up->ut_name,8);
nambuf[8] = '\0';
/*
# fetch an uid for that name (if possible), and see if it matches
*/
setpwent(); /* see getpwent(3) */
if ((ptr = getpwnam(up->ut_name)) == NULL) continue;
if (ptr->pw_uid == uid) return(up);
}
endpwent(); /* done for now */
return(NULL); /* no matching entry */
}
/*
# getutnam -- if the given user's name is logged into the system,
# a pointer is returned to a struct utmp; otherwise a NULL pointer is
# returned.
*/
struct utmp *getutnam(name)
char *name;
{
struct utmp *up;
if (setutent() == NULL) return(NULL);
while (up = getutent())
if (!strncmp(name,up->ut_name,8)) return(up);
return(NULL);
}
//E*O*F getutmp.c//
exit 0