/* Open and lock file.  Extract last record's number and
   record new record at end of file.  Unlock and close file.
   Usage: key=`fbup filename "command"`
   Outputs on stdout the key value of new last record in file.
   Relies on UNIX flock working.
   Relies on the command being less than 1000 characters long
*/
/*
  Started: RJ Botting, Sep 1999 SunOS ftp 4.1.3_U1 2 sun4m
  Advice and quick reveiw by Dr. Y. Karant.Review: Y Karant
*/
#define MAXBUF 1024


#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <sys/file.h>
#include <sys/types.h>
#include <unistd.h>

main( argc, argv)
int argc; char *argv[];
{
   int ans; /*answers to function calls*/
   int datafd; /* file descriptor */

   char line[MAXBUF];
   int i; /*number characters in line*/
   int lastkey, key;
   int noteof; /* not end of file yet*/
   char ch; /*last input charcter*/

   if(argc!=3){
	fprintf(stderr, "Usage: %s filename \"command\".\n", argv[0]);
	exit(1);
   }
   /*fprintf(stderr, "DBUG1: %s %s %s\n",argv[0], argv[1], argv[2]);*/
   datafd=open(argv[1], O_RDWR );
   if( -1 == datafd){
	fprintf(stderr, "Open %s failed with errno %d.\n", argv[1], errno);
	perror("");
	exit(1);
   }

   /*fprintf(stderr, "DBUG2: %s %s %s: about to try lock\n",argv[0], argv[1], argv[2]);*/

   ans= flock( datafd, LOCK_EX);
   if( -1 == ans ){
	    fprintf(stderr,
		    "File locking (flock) returned %d with errno %d!\n", ans, errno
	    );
	    perror("");
	    exit(2);
    }
   /*fprintf(stderr, "DBUG3: %s %s %s can access file\n", argv[0], argv[1], argv[2]);*/
  /*-----------------------*/
     /*start of data file*/
     noteof= read( datafd, &ch, 1);/*read ahead*/
     while(noteof){
	/*start of line*/
	i=0;

	while(noteof && ch!='\n' && i < MAXBUF - 1 ){ /*start char in line*/
		line[i]=ch;
		i++;
		noteof=read( datafd, &ch, 1);
	}/*end char in line*/

	while( noteof && ch!='\n' ){ /* char in rest of line*/
		noteof=read( datafd, &ch, 1);
	}/*end char in rest of line*/

	noteof=read( datafd, &ch, 1);/* end of line\n char*/
	/*end   of line*/

	line[i]='\0';
	i++;
	   /*fprintf(stderr, "DBUG7: line = %s\n", line);*/
     }/*end of file*/
   /*fprintf(stderr, "DBUG8: last line = %s\n", line);*/

   if( i == 0 || !sscanf(line, "%d", &lastkey) ){
	/*Wot! No number?*/
	lastkey=0;
   }

   key=lastkey+1;
     /*fprintf(stderr, "DBUG9: last key = %d, new key=%d\n", lastkey, key);*/

   /* Warning following doesn't check argv[2] is 
      less than MAXBUF-10 characters
   */
   sprintf(line, "%d %s\n", key, argv[2]);
       /*fprintf(stderr, "DBUGA: new line will be %s\n", line);*/
   lseek( datafd, 0, SEEK_END);
   write( datafd, line, strlen(line) );

   printf("%d\n", key);

  /*-----------------------*/
   /*fprintf(stderr, "DBUG4: %s %s %s: done it.\n", argv[0], argv[1], argv[2]);*/
   ans=flock( datafd, LOCK_UN);
   /*fprintf(stderr, "DBUG5: %s %s %s: flock( datafd, LOCK_UN) returns %d\n", argv[0], argv[1], argv[2], ans);*/
   if(ans== -1)perror("");
   ans=close(datafd);
   if(ans== -1)perror("");
   /*fprintf(stderr, "DBUG6: close returns %d\n", ans);*/
}