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#include <poll.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>
int
filter(char *input, size_t inlen, char *cmd, char **outputo, size_t *outleno)
{
char *output;
ssize_t outlen;
ssize_t outalloc = 4096;
pid_t pid;
output = malloc(outalloc);
outlen = 0;
int pipe0[2];
int pipe1[2];
if (pipe(pipe0) != 0 || pipe(pipe1) != 0)
goto fail;
char *argv[] = { "/bin/sh", "-c", cmd, (char *)0 };
if (!(pid = fork())) {
dup2(pipe0[0], 0);
close(pipe0[1]);
close(pipe0[0]);
dup2(pipe1[1], 1);
close(pipe1[0]);
close(pipe1[1]);
execvp(argv[0], argv);
exit(-1);
}
close(pipe0[0]);
close(pipe1[1]);
if (pid < 0) {
close(pipe0[1]);
close(pipe1[0]);
goto fail;
}
struct pollfd fds[2];
fds[0].fd = pipe1[0];
fds[0].events = POLLIN | POLLHUP;
fds[1].fd = pipe0[1];
fds[1].events = POLLOUT;
while ((fds[0].fd >= 0 || fds[1].fd >= 0) &&
poll(fds, sizeof fds / sizeof fds[0], -1) >= 0) {
if (fds[0].revents & POLLIN) {
if (outlen + 512 > outalloc) {
outalloc *= 2;
if (outalloc < 0)
exit(-1);
output = realloc(output, outalloc);
if (!output)
exit(-1);
}
ssize_t ret = read(fds[0].fd, output + outlen, 512);
if (ret > 0)
outlen += ret;
else
close(fds[0].fd);
} else if (fds[0].revents & (POLLERR | POLLHUP | POLLNVAL)) {
fds[0].fd = -1;
}
if (fds[1].revents & POLLOUT) {
ssize_t ret = write(fds[1].fd, input, inlen);
if (ret > 0) {
input += ret;
inlen -= ret;
}
if (ret <= 0 || inlen == 0)
close(fds[1].fd);
} else if (fds[1].revents & (POLLERR | POLLHUP | POLLNVAL)) {
fds[1].fd = -1;
}
}
// ok to fail when closed already
close(pipe0[1]);
close(pipe1[0]);
int status;
waitpid(pid, &status, 0);
*outputo = output;
*outleno = outlen;
return WEXITSTATUS(status);
fail:
*outputo = 0;
*outleno = 0;
free(output);
return -1;
}
#ifdef TEST
int
main()
{
char *input = "foo\nbar\nbaz";
int e;
char *output;
size_t outlen;
e = filter(input, strlen(input), "rev;exit 2", &output, &outlen);
fwrite(output, 1, outlen, stdout);
printf("%ld -> %d\n", outlen, e);
return 0;
}
#endif
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