💾 Archived View for thrig.me › blog › 2024 › 01 › 18 › bufferblock.c captured on 2024-02-05 at 10:55:28.
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#include <sys/wait.h>
#include <err.h>
#include <stdio.h>
#include <unistd.h>
#define ALOT 1024
#define CHILD 0
#define PIPE_READER 0
#define PIPE_WRITER 1
// the limit for my OpenBSD 7.4 system (AMD64) is just below this
#define TOPRINT 16385
char buf[ALOT];
int main(void) {
int bpipe[2], status;
pid_t pid;
size_t amount = 0, counter = 0;
if (pipe(bpipe) == -1) err(1, "pipe");
pid = fork();
if (pid < 0) err(1, "fork");
if (pid == CHILD) {
// wire up stdin to the pipe (only really needed if you
// were to exec off to some other program)
close(bpipe[PIPE_WRITER]);
if (dup2(bpipe[PIPE_READER], STDIN_FILENO) != STDIN_FILENO)
err(1, "dup");
close(bpipe[PIPE_READER]);
while (1) {
fprintf(stderr, "child waiting... %zu\n", counter++);
sleep(1);
}
errx(1, "fell off the loop??");
}
close(bpipe[PIPE_READER]);
while (amount < TOPRINT) {
write(bpipe[PIPE_WRITER], buf, ALOT);
amount += ALOT;
}
while (1) {
fprintf(stderr, "parent waiting... %zu\n", counter++);
waitpid(pid, &status, WNOHANG);
sleep(1);
}
errx(1, "child went away??");
}