minix/test/select/test11.c

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