我在看如何在手册页上使用pipe(2),但我不理解他们提供的源代码中的一行。
int
main(int argc, char *argv[])
{
int pipefd[2]; //Isn't this undefined??? so pipe(pipefd) would throw an error?
pid_t cpid;
char buf;
if (argc != 2) {
fprintf(stderr, "Usage: %s <string>\n", argv[0]);
exit(EXIT_FAILURE);
}
if (pipe(pipefd) == -1) {
perror("pipe");
exit(EXIT_FAILURE);
}
cpid = fork();
if (cpid == -1) {
perror("fork");
exit(EXIT_FAILURE);
}
if (cpid == 0) { /* Child reads from pipe */
close(pipefd[1]); /* Close unused write end */
while (read(pipefd[0], &buf, 1) > 0)
write(STDOUT_FILENO, &buf, 1);
write(STDOUT_FILENO, "\n", 1);
close(pipefd[0]);
_exit(EXIT_SUCCESS);
} else { /* Parent writes argv[1] to pipe */
close(pipefd[0]); /* Close unused read end */
write(pipefd[1], argv[1], strlen(argv[1]));
close(pipefd[1]); /* Reader will see EOF */
wait(NULL); /* Wait for child */
exit(EXIT_SUCCESS);
}
}
我以为非静态函数变量就是记忆中的东西?为什么这个源代码可以工作?
最佳答案
pipefd
这里数组用作输出参数,因此不需要初始化它。pipe
函数写入。