这个程序应该模拟一个关于带管道命令的posix shell。我尝试模拟并想要工作的例子是" ls | nl",但它没有,我无法弄清楚原因。我已经调试了这段代码很长时间没有成功。
我收到错误:" nl:输入错误:文件描述符错误",当我尝试不关闭任何文件描述符或只关闭一些文件描述符时(或者只关闭一些文件描述符)分叉,或只有父母等...),错误改变,或它的工作,但然后nl一直在等待输入。无论如何,我非常确定错误位于fork_cmd
或fork_cmds
,与close
有关。
我已经包含了所有代码。我知道parser.h没有任何问题。我知道这是非常糟糕的代码,但我认为它应该仍然有效。
我可能会失明,但如果有人能帮助我搞清楚,我会非常感激。希望这是我和其他人可以从中学到的东西。
#include "parser.h"
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <stdbool.h>
#define READ 0
#define WRITE 1
void fork_error() {
perror("fork() failed)");
exit(EXIT_FAILURE);
}
void close_error() {
perror("Couldn't close file descriptor");
exit(EXIT_FAILURE);
}
void fork_cmd(char* argv[], int n, int read_pipe[2], int write_pipe[2], int (*all_fds)[2]) {
pid_t pid;
switch (pid = fork()) {
case -1:
fork_error();
case 0:
if (read_pipe != NULL) {
if (dup2(read_pipe[READ], STDIN_FILENO) < 0) {
perror("Failed to redirect STDIN to pipe");
exit(EXIT_FAILURE);
}
}
if (write_pipe != NULL) {
if (dup2(write_pipe[WRITE], STDOUT_FILENO) < 0) {
perror("Failed to redirect STDOUT to pipe");
exit(EXIT_FAILURE);
}
}
for (int i = 0; i < n - 1; i++) {
if (close(all_fds[i][READ]) == -1 || close(all_fds[i][WRITE] == -1)) {
close_error();
}
}
execvp(argv[0], argv);
perror("execvp");
exit(EXIT_FAILURE);
default:
printf("Pid of %s: %d\n", argv[0], pid);
break;
}
}
void fork_cmds(char* argvs[MAX_COMMANDS][MAX_ARGV], int n, int (*fds)[2]) {
for (int i = 0; i < n; i++) {
if (n == 1) {
fork_cmd(argvs[i], n, NULL, NULL, fds);
}
// n > 1
else if (i == 0) {
fork_cmd(argvs[i], n, NULL, fds[i], fds);
}
else if (i == n - 1) {
fork_cmd(argvs[i], n, fds[i - 1], NULL, fds);
}
else {
fork_cmd(argvs[i], n, fds[i - 1], fds[i], fds);
}
}
for (int i = 0; i < n - 1; i++) {
if (close(fds[i][READ]) == -1 || close(fds[i][WRITE] == -1)) {
close_error();
}
}
}
void get_line(char* buffer, size_t size) {
getline(&buffer, &size, stdin);
buffer[strlen(buffer)-1] = '\0';
}
void wait_for_all_cmds(int n) {
// Not implemented yet!
for (int i = 0; i < n; i++) {
int status;
int pid;
if ((pid = wait(&status)) == -1) {
printf("Wait error");
} else {
printf("PARENT <%ld>: Child with PID = %ld and exit status = %d terminated.\n",
(long) getpid(), (long) pid, WEXITSTATUS(status));
}
}
}
int main() {
int n;
char* argvs[MAX_COMMANDS][MAX_ARGV];
size_t size = 128;
char line[size];
printf(" >> ");
get_line(line, size);
n = parse(line, argvs);
// Debug printouts.
printf("%d commands parsed.\n", n);
print_argvs(argvs);
int (*fds)[2] = malloc(sizeof(int) * 2 * (n - 1)); // should be pointer to arrays of size 2
for (int i = 0; i < n - 1; i++) {
if (pipe(fds[i]) == -1) {
perror("Creating pipe error"); // Creating pipe error: ...
exit(EXIT_FAILURE);
}
printf("pipe %d: read: %d, write: %d\n", i, fds[i][READ], fds[i][WRITE]);
}
fork_cmds(argvs, n, fds);
wait_for_all_cmds(n);
exit(EXIT_SUCCESS);
}
答案 0 :(得分:1)
问题是其中一个括号位于fork_cmd
和fork_cmds
的错误位置,当然应该是这样的:close(fds[i][WRITE])
。这是原始代码:
for (int i = 0; i < n - 1; i++) {
if (close(fds[i][READ]) == -1 || close(fds[i][WRITE] == -1))<--
{
close_error();
}
}