162 lines
4 KiB
C
162 lines
4 KiB
C
/*
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* Test name: test11.c
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*
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* Objetive: The purpose of this test is to make sure that select works
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* with pipes.
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*
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* Description: The select checks are divided in checks on writing for the
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* parent process, which has the writing end of the pipe, and checks on reading
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* and exception on the child process, which has the reading end of pipe. So
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* when the first process is ready to write to the pipe it will request a string
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* from the terminal and send it through the pipe. If the string is 'exit' then
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* the pipe is closed. The child process is blocked in a select checking for read
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* and exception. If there is data to be read then it will perform the read and
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* prints the read data. If the pipe is closed (user typed 'exit'), the child
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* process finishes.
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*
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* Jose M. Gomez
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*/
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#include <time.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <sys/asynchio.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <sys/select.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <limits.h>
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#include <string.h>
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#include <signal.h>
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void pipehandler(int sig)
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{
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}
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void do_child(int data_pipe[])
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{
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/* reads from pipe and prints out the data */
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char data[2048];
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int retval;
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fd_set fds_read;
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fd_set fds_exception;
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struct timeval timeout;
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signal(SIGPIPE, pipehandler);
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signal(SIGUSR1, pipehandler);
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/* first, close the write part of the pipe, since it is not needed */
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close(data_pipe[1]);
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while(1) {
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FD_ZERO(&fds_read);
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FD_ZERO(&fds_exception);
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FD_SET(data_pipe[0], &fds_read);
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FD_SET(data_pipe[0], &fds_exception);
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timeout.tv_sec = 5;
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timeout.tv_usec = 0;
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retval = select(data_pipe[0]+1, &fds_read, NULL, &fds_exception, &timeout);
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if (retval == -1) {
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perror("select");
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fprintf(stderr, "child: Error in select\n");
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continue;
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} else printf("child select: %d\n", retval);
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if (FD_ISSET(data_pipe[0], &fds_exception)) {
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printf("child: exception fd set. quitting.\n");
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break;
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}
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if (FD_ISSET(data_pipe[0], &fds_read)) {
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printf("child: read fd set. reading.\n");
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if ((retval = read(data_pipe[0], data, sizeof(data))) < 0) {
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perror("read");
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fprintf(stderr, "child: couldn't read from pipe\n");
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exit(-1);
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}
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if(retval == 0) {
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fprintf(stderr, "child: eof on pipe\n");
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break;
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}
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data[retval] = '\0';
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printf("pid %d Pipe reads (%d): %s\n", getpid(), retval, data);
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} else printf("child: no fd set\n");
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}
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/* probably pipe was broken, or got EOF via the pipe. */
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exit(0);
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}
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void do_parent(int data_pipe[])
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{
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char data[1024];
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int retval;
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fd_set fds_write;
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signal(SIGPIPE, pipehandler);
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signal(SIGUSR1, pipehandler);
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/* first, close the read part of pipe, since it is not needed */
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close(data_pipe[0]);
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/* now enter a loop of read user input, and writing it to the pipe */
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while (1) {
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FD_ZERO(&fds_write);
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FD_SET(data_pipe[1], &fds_write);
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printf("pid %d Waiting for pipe ready to write...\n", getpid());
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retval = select(data_pipe[1]+1, NULL, &fds_write, NULL, NULL);
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if (retval == -1) {
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perror("select");
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fprintf(stderr, "Parent: Error in select\n");
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exit(-1);
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}
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printf("Input data: ");
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if(!gets(data)) {
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printf("parent: eof; exiting\n");
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break;
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}
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if (!strcmp(data, "exit"))
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break;
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if (!FD_ISSET(data_pipe[1], &fds_write)) {
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fprintf(stderr, "parent: write fd not set?! retrying\n");
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continue;
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}
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retval = write(data_pipe[1], &data, 1024);
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if (retval == -1) {
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perror("write");
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fprintf(stderr, "Error writing on pipe\n");
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exit(-1);
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}
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}
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/* got exit from user */
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close(data_pipe[1]); /* close pipe, let child know we're done */
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wait(&retval);
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printf("Child exited with status: %d\n", retval);
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exit(0);
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}
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void main(void) {
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int pipes[2];
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int retval;
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int pid;
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/* create the pipe */
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retval = pipe(pipes);
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if (retval == -1) {
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perror("pipe");
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fprintf(stderr, "Error creating the pipe\n");
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exit(-1);
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}
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pid = fork();
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if (pid == -1) {
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fprintf(stderr, "Error forking\n");
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exit(-1);
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}
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if (pid == 0) /* child proc */
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do_child(pipes);
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else
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do_parent(pipes);
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}
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