Could anyone tell me what's wrong with this code?
In summary, it creates input and output pipes and fork-exec's the sort
program. The parent reads the dictionary /usr/share/dict/words
and writes it to the pipe that is dup2()
'd to sort
's standard in and, likewise, reads the output from it, printing it to the terminal (the standard output of the parent). Or, at least, that's what's supposed to be happening.
A backtrace says that the parent hangs at the read()
on line 130 (marked with the comment 'XXX'). It's almost as though sort
isn't aware of the end-of-file, but closing the write end of pipeIn
should 'signal' this, right?
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
int main(int argc, char** argv)
{
int pipeIn[2];
int pipeOut[2];
if ((pipe(pipeIn)) == -1)
{
perror("pipe");
exit(EXIT_FAILURE);
}
if ((pipe(pipeOut)) == -1)
{
perror("pipe");
exit(EXIT_FAILURE);
}
pid_t child = fork();
if (child == 0)
{
// This is child!
if ((dup2(pipeIn[0], STDIN_FILENO)) == -1)
{
perror("dup2");
exit(EXIT_FAILURE);
}
if ((dup2(pipeOut[1], STDOUT_FILENO)) == -1)
{
perror("dup2");
exit(EXIT_FAILURE);
}
if ((dup2(pipeOut[1], STDERR_FILENO)) == -1)
{
perror("dup2");
exit(EXIT_FAILURE);
}
if ((close(pipeIn[0])) == -1)
{
perror("close");
exit(EXIT_FAILURE);
}
if ((close(pipeOut[1])) == -1)
{
perror("close");
exit(EXIT_FAILURE);
}
if ((execlp("sort", "-r", NULL)) == -1)
{
perror("execlp");
exit(EXIT_FAILURE);
}
}
else if (child == -1)
{
perror("fork");
exit(EXIT_FAILURE);
}
else
{
// This is parent!
if ((close(pipeIn[0])) == -1)
{
perror("close");
exit(EXIT_FAILURE);
}
if ((close(pipeOut[1])) == -1)
{
perror("close");
exit(EXIT_FAILURE);
}
int dict = open("/usr/share/dict/words", O_RDONLY);
if (dict == -1)
{
perror("open");
exit(EXIT_FAILURE);
}
char buf[1024];
int count;
while ((count = read(dict, buf, sizeof(char) * 1024)) > 0)
{
putchar('.');
if ((write(pipeIn[1], buf, count)) == -1)
{
perror("write 1");
exit(EXIT_FAILURE);
}
}
if (count == -1)
{
perror("read");
exit(EXIT_FAILURE);
}
if ((close(dict)) == -1)
{
perror("close");
exit(EXIT_FAILURE);
}
if ((close(pipeIn[1])) == -1)
{
perror("close");
exit(EXIT_FAILURE);
}
while ((count = read(pipeOut[0], buf, sizeof(char) * 1024)) > 0) // XXX
{
putchar('!');
if ((write(STDOUT_FILENO, buf, count)) == -1)
{
perror("write 2");
exit(EXIT_FAILURE);
}
}
if (count == -1)
{
perror("read");
exit(EXIT_FAILURE);
}
if ((close(pipeOut[0])) == -1)
{
perror("close");
exit(EXIT_FAILURE);
}
}
return EXIT_SUCCESS;
}
Thank you for any input (pardon the pun).