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#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <errno.h>
#include <signal.h>
#include <unistd.h>
#include <fcntl.h>
#include <wait.h>
#include <poll.h>
#define ARGV0 "subproc"
#define STDIO_BUFSIZE 4096
#define DELIM '\n' // -print0 option
struct child {
pid_t pid;
struct {
int in;
int out;
int err;
} std;
};
struct pbuf {
char buf[STDIO_BUFSIZE];
size_t len;
int fd;
};
static bool setnonblock (const int fd, const bool set) {
int fr;
fr = fcntl(fd, F_GETFL, 0);
if (fr < 0) {
return false;
}
if (set) {
fr |= O_NONBLOCK;
}
else {
fr &= ~O_NONBLOCK;
}
return fcntl(fd, F_SETFL, fr) >= 0;
}
static size_t do_output (const int fd, char *buf, size_t len) {
char *end;
size_t outlen;
end = memrchr(buf, DELIM, len);
if (end == NULL) {
// one problem with this: buf getting full
write(fd, buf, len);
return len;
}
outlen = end - buf + 1;
write(fd, buf, outlen);
return outlen;
}
int main (const int argc, const char **argv) {
const size_t nb_procs = argc - 1;
const size_t nb_pfds = nb_procs * 2;
int ec = 0;
struct child subprocs[nb_procs];
struct pollfd pfds[nb_pfds];
struct pbuf pbufs[nb_pfds];
size_t nb_hup;
int s;
memset(subprocs, 0, sizeof(subprocs));
memset(pfds, 0, sizeof(pfds));
memset(pbufs, 0, sizeof(pbufs));
for (size_t i = 0; i < nb_pfds; i += 1) {
pbufs[i].fd = -1;
}
if (argc == 1) {
fprintf(stderr, "Usage: "ARGV0" <DIR> [DIR ...]\n");
return 2;
}
for (int i = 0, j = 0; i < argc - 1; i += 1, j += 2) {
const char *path = argv[i + 1];
struct child *sp = subprocs + i;
struct {
int in[2];
int out[2];
int err[2];
} p;
if (pipe(p.in) != 0 || pipe(p.out) != 0 || pipe(p.err) != 0) {
perror(ARGV0": pipe()");
return 1;
}
sp->pid = fork();
if (sp->pid > 0) {
close(p.in[0]);
close(p.out[1]);
close(p.err[1]);
sp->std.in = p.in[1];
pfds[j].fd = sp->std.out = p.out[0];
pfds[j + 1].fd = sp->std.err = p.err[0];
pfds[j].events = pfds[j + 1].events = POLLIN;
pbufs[j].fd = STDOUT_FILENO;
pbufs[j + 1].fd = STDERR_FILENO;
setnonblock(sp->std.in, true);
setnonblock(sp->std.out, true);
setnonblock(sp->std.err, true);
}
else if (sp->pid == 0) {
const char *new_argv[] = { "find", path, NULL };
close(p.in[1]);
close(p.out[0]);
close(p.err[0]);
sp->std.in = p.in[0];
sp->std.out = p.out[1];
sp->std.err = p.err[1];
if (dup2(sp->std.in, STDIN_FILENO) < 0 ||
dup2(sp->std.out, STDOUT_FILENO) < 0 ||
dup2(sp->std.err, STDERR_FILENO) < 0)
{
perror(ARGV0": dup2()");
abort();
}
close(sp->std.in);
close(sp->std.out);
close(sp->std.err);
execvp("find", (char*const*)new_argv);
perror(ARGV0": execvp()");
abort();
}
else {
perror(ARGV0": fork()");
return 1;
}
}
nb_hup = 0;
while (nb_hup < nb_pfds) {
int fr;
fr = poll(pfds, (nfds_t)nb_pfds, -1);
if (fr == 0) {
// should never reach unless poll() was called w/ timeout
break;
}
else if (fr < 0) {
perror(ARGV0": poll()");
abort();
}
for (size_t i = 0; i < nb_pfds; i += 1) {
struct pollfd *pfd = pfds + i;
if (pfd->revents == 0) {
continue;
}
if (pfd->revents & POLLIN) {
struct pbuf *pb = pbufs + i;
const size_t iofr = read(
pfd->fd,
pb->buf + pb->len,
sizeof(pb->buf) - pb->len);
if (iofr > 0) {
size_t outlen;
size_t rem;
pb->len += (size_t)iofr;
outlen = do_output(pb->fd, pb->buf, pb->len);
rem = pb->len - outlen;
memmove(pb->buf, pb->buf + outlen, rem);
pb->len = rem;
}
else if (iofr == 0) {
do_output(pb->fd, pb->buf, pb->len);
pb->len = 0;
}
else {
perror(ARGV0": read()");
abort();
}
}
else if (pfd->revents & POLLHUP) {
pfd->fd = -1;
nb_hup += 1;
}
}
}
while (wait(&s) >= 0) {
if (WIFSIGNALED(s) || WEXITSTATUS(s) != 0) {
ec = 1;
}
}
return ec;
}
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