/** * apr tutorial sample code * http://dev.ariel-networks.com/apr/ */#ifdef HAVE_CONFIG_H#include <config.h>#endif#include <stdio.h>#include <stdlib.h>#include <assert.h>#include <apr_general.h>#include <apr_file_io.h>static apr_status_t do_writelock(const char *fname, apr_pool_t *mp){    apr_status_t rv;    apr_file_t *fp;        if ((rv = apr_file_open(&fp, fname, APR_WRITE, APR_OS_DEFAULT, mp)) != APR_SUCCESS) {        return rv;    }    rv = apr_file_lock(fp, APR_FLOCK_EXCLUSIVE | APR_FLOCK_NONBLOCK);    /* if you specify APR_FLOCK_NONBLOCK flag, apr_file_lock() would fail.     * you should check the return value */    if (rv != APR_SUCCESS) {        puts("writable-lock failed");        goto done;    }    printf("%s is writable locked. press any key to unlock\n", fname);    getchar();    apr_file_unlock(fp); done:    apr_file_close(fp);    return rv;}static apr_status_t do_readlock(const char *fname, apr_pool_t *mp){    apr_status_t rv;    apr_file_t *fp;    if ((rv = apr_file_open(&fp, fname, APR_READ,  APR_OS_DEFAULT, mp)) != APR_SUCCESS) {        return rv;    }    rv = apr_file_lock(fp, APR_FLOCK_SHARED | APR_FLOCK_NONBLOCK);    if (rv != APR_SUCCESS) {        puts("readable-lock failed");        goto done;    }    apr_file_unlock(fp); done:    apr_file_close(fp);    return rv;}/** * file lock sample code * @remark Error checks omitted */int main(int argc, const char *argv[]){    apr_status_t rv;    apr_pool_t *mp;    int c;    const char *fname;            if (argc < 2) {        printf("usage %s output-filename\n", argv[0]);        return 0;    }    fname = argv[1];    apr_initialize();    apr_pool_create(&mp, NULL);    puts("writable-lock / readable-lock [w/r]?");    c = getchar();    if (c == 'w') {        rv = do_writelock(fname, mp);    } else if (c == 'r') {        rv = do_readlock(fname, mp);    }    apr_pool_destroy(mp);    apr_terminate();    return 0;}