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 */
showLocksInRange(int fd,off_t lwr,off_t upr)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
main(int argc,char ** argv)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