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 } 100