tool/showlocks.c

   1 /*
   2 ** This file implements a simple command-line utility that shows all of the
   3 ** Posix Advisory Locks on a file.
   4 **
   5 ** Usage:
   6 **
   7 **     showlocks FILENAME
   8 **
   9 ** To compile:  gcc -o showlocks showlocks.c
  10 */
  11 #include <stdio.h>
  12 #include <unistd.h>
  13 #include <fcntl.h>
  14 #include <stdlib.h>
  15 #include <string.h>
  16
  17 /* This utility only looks for locks in the first 2 billion bytes */
  18 #define MX_LCK 2147483647
  19
  20 /*
  21 ** Print all locks on the inode of "fd" that occur in between
  22 ** lwr and upr, inclusive.
  23 */
  24 static int showLocksInRange(int fd, off_t lwr, off_t upr){
  25   int cnt = 0;
  26   struct flock x;
  27
  28   x.l_type = F_WRLCK;
  29   x.l_whence = SEEK_SET;
  30   x.l_start = lwr;
  31   x.l_len = upr-lwr;
  32   fcntl(fd, F_GETLK, &x);
  33   if( x.l_type==F_UNLCK ) return 0;
  34   printf("start: %-12d len: %-5d pid: %-5d type: %s\n",
  35        (int)x.l_start, (int)x.l_len,
  36        x.l_pid, x.l_type==F_WRLCK ? "WRLCK" : "RDLCK");
  37   cnt++;
  38   if( x.l_start>lwr ){
  39     cnt += showLocksInRange(fd, lwr, x.l_start-1);
  40   }
  41   if( x.l_start+x.l_len<upr ){
  42     cnt += showLocksInRange(fd, x.l_start+x.l_len+1, upr);
  43   }
  44   return cnt;
  45 }
  46
  47 int main(int argc, char **argv){
  48   int fd;
  49   int cnt;
  50
  51   if( argc!=2 ){
  52     fprintf(stderr, "Usage: %s FILENAME\n", argv[0]);
  53     return 1;
  54   }
  55   fd = open(argv[1], O_RDWR, 0);
  56   if( fd<0 ){
  57     fprintf(stderr, "%s: cannot open %s\n", argv[0], argv[1]);
  58     return 1;
  59   }
  60   cnt = showLocksInRange(fd, 0, MX_LCK);
  61   if( cnt==0 ) printf("no locks\n");
  62   close(fd);
  63   return 0;
  64 }