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100 lines
2.3 KiB
C
100 lines
2.3 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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struct lockRange {
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off_t lwr;
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off_t upr;
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} *aPending = 0;
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int nAlloc = 1;
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int nPending = 0;
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int nDone = 0;
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nPending = 1;
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aPending = malloc( sizeof(aPending[0]) );
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if( aPending==0 ){
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fprintf(stderr, "out of memory\n");
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exit(1);
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}
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aPending[0].lwr = lwr;
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aPending[0].upr = upr;
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for(nDone=0; nDone<nPending; nDone++){
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lwr = aPending[nDone].lwr;
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upr = aPending[nDone].upr;
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if( lwr>=upr ) continue;
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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 ) continue;
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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( nPending+2 > nAlloc ){
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nAlloc = nAlloc*2 + 2;
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aPending = realloc(aPending, sizeof(aPending[0])*nAlloc );
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}
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if( aPending==0 ){
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fprintf(stderr, "unable to realloc for %d bytes\n",
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(int)sizeof(aPending[0])*(nPending+2));
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exit(1);
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}
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if( lwr<x.l_start ){
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aPending[nPending].lwr = lwr;
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aPending[nPending].upr = x.l_start;
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nPending++;
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}
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if( x.l_start+x.l_len<=upr ){
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aPending[nPending].lwr = x.l_start + x.l_len;
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aPending[nPending].upr = upr;
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nPending++;
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}
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}
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free(aPending);
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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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