65 lines
1.4 KiB
C
65 lines
1.4 KiB
C
/*
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** This file implements a simple command-line utility that shows all of the
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** Posix Advisory Locks on a file.
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**
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** Usage:
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**
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** showlocks FILENAME
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**
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** To compile: gcc -o showlocks showlocks.c
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*/
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#include <stdio.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include <string.h>
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/* This utility only looks for locks in the first 2 billion bytes */
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#define MX_LCK 2147483647
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/*
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** Print all locks on the inode of "fd" that occur in between
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** lwr and upr, inclusive.
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*/
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static int showLocksInRange(int fd, off_t lwr, off_t upr){
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int cnt = 0;
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struct flock x;
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x.l_type = F_WRLCK;
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x.l_whence = SEEK_SET;
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x.l_start = lwr;
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x.l_len = upr-lwr;
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fcntl(fd, F_GETLK, &x);
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if( x.l_type==F_UNLCK ) return 0;
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printf("start: %-12d len: %-5d pid: %-5d type: %s\n",
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(int)x.l_start, (int)x.l_len,
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x.l_pid, x.l_type==F_WRLCK ? "WRLCK" : "RDLCK");
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cnt++;
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if( x.l_start>lwr ){
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cnt += showLocksInRange(fd, lwr, x.l_start-1);
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}
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if( x.l_start+x.l_len<upr ){
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cnt += showLocksInRange(fd, x.l_start+x.l_len+1, upr);
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}
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return cnt;
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}
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int main(int argc, char **argv){
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int fd;
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int cnt;
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if( argc!=2 ){
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fprintf(stderr, "Usage: %s FILENAME\n", argv[0]);
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return 1;
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}
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fd = open(argv[1], O_RDWR, 0);
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if( fd<0 ){
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fprintf(stderr, "%s: cannot open %s\n", argv[0], argv[1]);
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return 1;
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}
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cnt = showLocksInRange(fd, 0, MX_LCK);
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if( cnt==0 ) printf("no locks\n");
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close(fd);
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return 0;
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}
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