144 lines
3.2 KiB
C
144 lines
3.2 KiB
C
/*
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* SPDX-License-Identifier: MIT
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* Copyright (c) 2025 Fabio Scotto di Santolo
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*/
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/select.h>
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#include <sys/time.h>
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#include <unistd.h>
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#define FILE_NUMBER 3
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#define FILENAME_MAX_LEN 10
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#define TIMEOUT 10
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#define BUF_LEN 1024
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int create_tmp_file(char *filename);
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void cleanup(char *filenames[]);
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int main(void)
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{
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int exit_code = 0;
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char *filename_template = "test%d.txt";
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char *filenames[FILE_NUMBER] = {NULL};
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int fds[FILE_NUMBER] = {0};
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// Create a bunch of number ephemeral files
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for (int i = 0; i < FILE_NUMBER; i++) {
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char *filename =
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(char *)malloc(FILENAME_MAX_LEN * sizeof(char));
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if (!filename) {
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perror("malloc failed");
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exit_code = -1;
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goto exit;
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}
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snprintf(filename, FILENAME_MAX_LEN, filename_template, i + 1);
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filenames[i] = filename;
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printf("Opening file %s...\n", filename);
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fds[i] = create_tmp_file(filename);
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if (fds[i] == -1) {
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fprintf(stderr, "Error to open file %s: %s\n", filename,
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strerror(errno));
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exit_code = -1;
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goto exit;
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}
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printf("Open file %s with file descriptor %d\n", filename,
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fds[i]);
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// write something in the files
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dprintf(fds[i], "Hello I am %s\n", filename);
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}
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fd_set readfds;
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FD_ZERO(&readfds);
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for (int i = 0; i < FILE_NUMBER; i++) {
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FD_SET(fds[i], &readfds);
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}
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struct timeval *timeout =
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(struct timeval *)malloc(sizeof(struct timeval));
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timeout->tv_sec = TIMEOUT;
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timeout->tv_usec = 0;
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/* This function do not work with regular files because for the
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* operating system, a regular file is ready always. This example is
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* wrong the best way to use select() is with socket, pipe or other
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* channel types.
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*/
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int ret = select(FILE_NUMBER + 1, &readfds, NULL, NULL, timeout);
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if (ret == -1) {
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fprintf(stderr, "Error to select: %s\n", strerror(errno));
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exit_code = 1;
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goto exit;
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} else if (!ret) {
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fprintf(stderr, "%d seconds elapsed.\n", TIMEOUT);
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exit_code = 1;
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goto exit;
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}
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for (int i = 0; i < FILE_NUMBER; i++) {
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int fd = fds[i];
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if (FD_ISSET(fd, &readfds)) {
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char buf[BUF_LEN + 1];
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int len = read(fd, buf, BUF_LEN);
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if (len == -1) {
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fprintf(stderr, "Error reading file %s: %s\n",
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filenames[i], strerror(errno));
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exit_code = 1;
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goto exit;
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}
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if (len) {
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buf[len] = '\0';
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printf("%s:\n%s\n", filenames[i], buf);
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}
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}
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}
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exit:
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// Closing and remove all creating files
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for (int i = 0; i < FILE_NUMBER; i++) {
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int fd = fds[i];
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printf("Close file with file descriptor %d\n", fd);
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if (close(fd) == -1) {
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fprintf(stderr, "Error to close file %d: %s\n", fd,
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strerror(errno));
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}
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}
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free(timeout);
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timeout = NULL;
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printf("Cleanup files\n");
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cleanup(filenames);
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return exit_code;
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}
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int create_tmp_file(char *filename)
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{
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int fd = open(filename, O_CREAT | O_EXCL | O_RDWR, 0644);
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if (fd == -1) {
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return -1;
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}
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return fd;
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}
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void cleanup(char *filenames[])
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{
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for (int j = 0; j < FILE_NUMBER; j++) {
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if (filenames[j] != NULL) {
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if (remove(filenames[j]) == -1)
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fprintf(stderr, "Failed to remove %s: %s\n",
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filenames[j], strerror(errno));
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free(filenames[j]);
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filenames[j] = NULL;
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}
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}
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}
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