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   struct lockRange {
  28     off_t lwr;
  29     off_t upr;
  30   } *aPending = 0;
  31   int nAlloc = 1;
  32   int nPending = 0;
  33   int nDone = 0;
  34
  35   nPending = 1;
  36   aPending = malloc( sizeof(aPending[0]) );
  37   if( aPending==0 ){
  38     fprintf(stderr, "out of memory\n");
  39     exit(1);
  40   }
  41   aPending[0].lwr = lwr;
  42   aPending[0].upr = upr;
  43
  44   for(nDone=0; nDone<nPending; nDone++){
  45     lwr = aPending[nDone].lwr;
  46     upr = aPending[nDone].upr;
  47     if( lwr>=upr ) continue;
  48     x.l_type = F_WRLCK;
  49     x.l_whence = SEEK_SET;
  50     x.l_start = lwr;
  51     x.l_len = upr - lwr;
  52     fcntl(fd, F_GETLK, &x);
  53     if( x.l_type==F_UNLCK ) continue;
  54     printf("start: %-12d len: %-5d pid: %-5d type: %s\n",
  55          (int)x.l_start, (int)x.l_len,
  56          x.l_pid, x.l_type==F_WRLCK ? "WRLCK" : "RDLCK");
  57     cnt++;
  58     if( nPending+2 > nAlloc ){
  59       nAlloc = nAlloc*2 + 2;
  60       aPending = realloc(aPending, sizeof(aPending[0])*nAlloc );
  61     }
  62     if( aPending==0 ){
  63       fprintf(stderr, "unable to realloc for %d bytes\n",
  64                       (int)sizeof(aPending[0])*(nPending+2));
  65       exit(1);
  66     }
  67     if( lwr<x.l_start ){
  68       aPending[nPending].lwr = lwr;
  69       aPending[nPending].upr = x.l_start;
  70       nPending++;
  71     }
  72     if( x.l_start+x.l_len<=upr ){
  73       aPending[nPending].lwr = x.l_start + x.l_len;
  74       aPending[nPending].upr = upr;
  75       nPending++;
  76     }
  77   }
  78   free(aPending);
  79   return cnt;
  80 }
  81
  82 int main(int argc, char **argv){
  83   int fd;
  84   int cnt;
  85
  86   if( argc!=2 ){
  87     fprintf(stderr, "Usage: %s FILENAME\n", argv[0]);
  88     return 1;
  89   }
  90   fd = open(argv[1], O_RDWR, 0);
  91   if( fd<0 ){
  92     fprintf(stderr, "%s: cannot open %s\n", argv[0], argv[1]);
  93     return 1;
  94   }
  95   cnt = showLocksInRange(fd, 0, MX_LCK);
  96   if( cnt==0 ) printf("no locks\n");
  97   close(fd);
  98   return 0;
  99 }