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fdtool.c
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fdtool.c
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#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
int ownout = STDOUT_FILENO;
void die() {
exit(1);
}
void die_usage() {
fprintf(fdopen(ownout, "a"), "Usage: fdtool [--pipe fdread fdwrite]* -- program [option]*\n");
exit(1);
}
int is_opened(int fd) {
if (fcntl(fd, F_GETFD) < 0) {
if (errno == EBADF)
return 0;
return -errno;
}
return 1;
}
void create_pipe(int fdi, int fdo) {
int p[2];
if (is_opened(fdi) || is_opened(fdo))
die();
if (dup2(2, fdi) < 0 || dup2(2, fdo) < 0)
die();
if (pipe(p) < 0)
die();
if (dup2(p[0], fdi) < 0 || dup2(p[1], fdo) < 0)
die();
if (close(p[0]) < 0 || close(p[1]) < 0)
die();
}
int main (int argc, char** argv) {
int i = 1;
for (; i < argc; ) {
if (!strcmp("--", argv[i])) {
if (i + 1 > argc)
die_usage();
if (execvp(argv[i + 1], argv + i + 1) < 0)
return 1;
} else if (!strcmp("--pipe", argv[i])) {
if (i + 2 > argc)
die_usage();
create_pipe(atoi(argv[i + 1]), atoi(argv[i + 2]));
i += 3;
} else
die_usage();
}
die_usage();
return 0;
}