/*
 * cc -o checklist checklist.c -lnsl
 *
 * note: search for JDS and change the two printf's on systems
 *       that support lock.l_sysid
 */

#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <netdb.h>

static char addrbuf[128];

main(argc,argv)
int argc;
char **argv;
{
 int fdread,fdwrite;
 struct flock lock;
 static char *getname();

 if (argc != 2)
 {
    printf("Usage: checklock <filename>\n");
    exit(1);
 }

 if ((fdread = open(*++argv,O_RDONLY)) < 0)
 {
    perror("Unable to open file for read");
    exit(2);
 }

 fdwrite = open(*argv,O_RDWR);

 lock.l_whence = 0;
 lock.l_start  = 0L;
 lock.l_len = 0;
 lock.l_type = F_RDLCK;
 if (fcntl(fdread,F_GETLK,(void *)&lock) < 0)
 {
    perror("fcn;t failed on read lock");
    exit(3);
 }

 if (lock.l_type == F_UNLCK)
 {
    printf("Read lock is available.\n");
 }
 else
 {
    /* JDS
    printf("Read lock is blocked by %d on %s.\n",lock.l_pid,
	    getname(lock.l_sysid));
    */
    printf("Read lock is blocked by %d\n",lock.l_pid);
 }

 if (fdwrite >= 0)
 {
    lock.l_whence = 0;
    lock.l_start  = 0L;
    lock.l_len = 0;
    lock.l_type = F_WRLCK;
    if (fcntl(fdread,F_GETLK,(void *)&lock) < 0)
    {
       perror("fcn;t failed on read lock");
       exit(4);
    }

    if (lock.l_type == F_UNLCK)
    {
       printf("Write lock is available.\n");
    }
    else
    {
       /* JDS
       printf("Write lock is blocked by %d on %s.\n",lock.l_pid,
	      getname(lock.l_sysid));
       */
       printf("Write lock is blocked by %d.\n",lock.l_pid);
    }
 }
 exit(0);
}

static char *getname(sysid)
unsigned long sysid;
{
 struct hostent *node;

 if (sysid)
 {
    if (node = gethostbyaddr((char *)&sysid,sizeof(sysid),AF_INET))
    {
       return(node->h_name);
    }
    else
    {
       sprintf(addrbuf,"%2.2d.%2.2d.%2.2d.%2.2d",
	       (sysid >> 24),
	       (sysid & 0x00FF0000) >> 16,
	       (sysid & 0x0000FF00) >> 8,
	       (sysid & 0x000000FF));
       return(addrbuf);
    }
 }
 else
 {
    return("current system");
 }
}