Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!cis.ohio-state.edu!ucbvax!agate!usenet
From: izumi@pinoko.berkeley.edu (Izumi Ohzawa)
Newsgroups: comp.sys.next
Subject: Trimmer for /usr/adm/wtmp
Message-ID: <1991Jun19.022344.26696@agate.berkeley.edu>
Date: 19 Jun 91 02:23:44 GMT
Sender: usenet@agate.berkeley.edu (USENET Administrator)
Reply-To: izumi@pinoko.berkeley.edu
Organization: University of California, Berkeley
Lines: 118

Here's a little more reasonable file trimmer for /usr/adm/wtmp file.
With the default monthly script (/usr/adm/monthly), the wtmp file
is wiped clean on the first of each month.  It also wipes out
/usr/adm/lastlog, which shouldn't be necessary (lastlog doesn't grow).

-------- cut here -----
/* Program:  wtmptrim -- trims the size of /usr/adm/wtmp file by keeping the  
last N entries.
* Usage:     wtmptrim [numentries]
	where numentries defaults to 2000 entries.

* Valid for 1.0, 2.0, 2.1

* Compile:    cc -O -o wtmptrim wtmptrim.c
	      strip wtmptrim

* Install wtmptrim in /usr/local/bin.
* Modify /usr/adm/monthly as below:
-----------------------------------------------------------------
*** monthly.old Tue Jun 18 18:46:43 1991
--- monthly     Tue Jun 18 18:50:05 1991
***************
*** 5,15 ****
  # commands in here, like pruning of log files
  #
  
! # Trim the lastlog
! cp -p /usr/adm/lastlog /usr/adm/lastlog.old
! cat /dev/null > /usr/adm/lastlog
  
! # Trim wtmp
! cp -p /usr/adm/wtmp /usr/adm/wtmp.old
! cat /dev/null > /usr/adm/wtmp
! 
--- 5,13 ----
  # commands in here, like pruning of log files
  #
  
! # NO NEED to trim the lastlog
! # cp -p /usr/adm/lastlog /usr/adm/lastlog.old
! # cat /dev/null > /usr/adm/lastlog
  
! # Trim wtmp to the last 2000 entries
! /usr/local/bin/wtmptrim 2000
-----------------------------------------------------------------
*/

#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <utmp.h>
#include <sys/stat.h>

#define DEF_ENTRIES	2000
#define MAXENTRIES	100000
#define MINENTRIES	100
#define WTMPFILE	"/usr/adm/wtmp"
#define TEMPFILE	"/usr/adm/wtmp.new"
#define WTMPOLD		"/usr/adm/wtmp.old"


void main(int argc, char *argv[])
{
int i;
int numtrim = DEF_ENTRIES;
int numcurrent, nemptyto;
FILE *fin_wtmp, *fout_wtmp;
struct stat filestat;
struct utmp s_utmp;

	if(argc > 1) {
		/* if argument is given, interpret argv[1] as numentries */
		i = atoi(argv[1]);
		if(i > MINENTRIES && i <= MAXENTRIES )
			numtrim = i;		/* defaults to DEF_ENTRIES */
	}

	if(stat(WTMPFILE, &filestat)) {
		printf("Can't get stat for file: %s\n", WTMPFILE);
		exit(1);
	}
	else {
	    numcurrent = filestat.st_size / sizeof(s_utmp);
    	    if(numcurrent <= numtrim)
		exit(0);			/* Small, no need to trim file  
*/
	    nemptyto = numcurrent - numtrim;	/* Empty this many records */
	    if ((fin_wtmp = fopen(WTMPFILE, "r")) != NULL &&
	            (fout_wtmp = fopen(TEMPFILE, "w")) != NULL) {
		for(i=0; i<nemptyto; i++)				/*  
Discard old stuff */
		    fread(&s_utmp, sizeof(s_utmp), 1, fin_wtmp);
		while(fread(&s_utmp, sizeof(s_utmp), 1, fin_wtmp))	/* Now,  
copy the rest */
		    fwrite(&s_utmp, sizeof(s_utmp), 1, fout_wtmp);
		(void) fclose(fin_wtmp);
		(void) fclose(fout_wtmp);
		(void) rename(WTMPFILE, WTMPOLD);		/* current one  
to .old */
		(void) rename(TEMPFILE, WTMPFILE);		/* trimmed one  
to wtmp file */
	    }
	    else {
	        printf("Can't open file(s): %s and/or %s\n", WTMPFILE,  
TEMPFILE);
		exit(2);
	    }
	}
	exit(0);
}

-------- cut here -----

Izumi Ohzawa             [ $@Bg_78^=;(J ]
USMail: University of California, 360 Minor Hall, Berkeley, CA 94720
Telephone: (415) 642-6440     Fax:  (415) 642-3323
Standard mail: izumi@violet.berkeley.edu
NeXTmail:      izumi@pinoko.berkeley.edu