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 } 65