86 lines
1.6 KiB
C
86 lines
1.6 KiB
C
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#include <sys/wait.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 <unistd.h>
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int pipefd[2];
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int
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main(void)
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{
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if (pipe(pipefd) != 0) {
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perror("pipe");
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return EXIT_FAILURE;
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}
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int pwrite = pipefd[1];
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int pread = pipefd[0];
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pid_t pid = fork();
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if (pid < 0) {
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perror("fork");
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return EXIT_FAILURE;
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}
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/* the first child */
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else if (pid == 0) {
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/*
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* Close standard output and reassign it to the pipe.
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* The close is done automagically by dup2.
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*/
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dup2(pwrite, STDOUT_FILENO);
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/* Close unnecessary pipe read file descriptor. */
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close(pread);
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/* Now we do the thing. */
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printf("Hello, world.\n");
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/* ¡Adios! */
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return EXIT_SUCCESS;
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}
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/*
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* We are now in the parent. We must fork again, and do the
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* child dance.
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*/
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if ((pid = fork()) < 0) {
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perror("fork");
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return EXIT_FAILURE;
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}
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/* the second of the children */
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else if (pid == 0) {
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/* Close standard input and reassign it to the pipe. */
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dup2(pread, STDIN_FILENO);
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/* Close unnecessary pipe write file descriptor. */
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close(pwrite);
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/* Read the thing. */
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char data[16];
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ssize_t rl;
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memset(data, 0, 16);
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rl = read(STDIN_FILENO, data, 15);
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if (rl < 1) {
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perror("read");
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return EXIT_FAILURE;
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}
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printf("%s", data);
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return EXIT_SUCCESS;
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}
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/* wait for the children to die so we can reap them */
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/* there are two, they should drop dead on their own. */
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int status1, status2;
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waitpid(-1, &status1, 0);
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waitpid(-1, &status2, 0);
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if (WIFEXITED(status1) && WIFEXITED(status2)) {
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printf("Goodbye.\n");
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return EXIT_SUCCESS;
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}
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fprintf(stderr, "At least one child died abnormally.\n");
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return EXIT_FAILURE;
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}
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