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#include <stdio.h>
#include <stdlib.h>
#include <err.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
/**
* NOTE: requires fdescfs to be mounted to run interpreted files (starting with #!)
*/
#define DEFAULT_FD 3
char *args[] = { "batchrun", NULL };
void
set_async(int fd, int on)
{
int flags;
if ((flags = fcntl(fd, F_GETFL)) == -1)
err(1, "fcntl()");
if (on) {
flags |= O_NONBLOCK;
} else {
flags &= ~O_NONBLOCK;
}
if (fcntl(fd, F_SETFL, flags) == -1)
err(1, "fcntl()");
}
int
main(int argc, char **argv)
{
char buf[2], *end = NULL;
ssize_t ret;
int tries = 0, fd = DEFAULT_FD;
if (argc > 1) {
fd = strtol(argv[1], &end, 10);
if (end == argv[1])
errx(1, "Filedescriptor supplied (\"%s\") is not a number", argv[1]);
}
set_async(fd, 1);
retry:
if (tries++ >= 3)
errx(1, "Failed to read file header");
ret = pread(fd, buf, sizeof(buf), 0);
if (ret == 2) {
if (strncmp(buf, "#!", 2) != 0) {
fcntl(fd, F_SETFD, FD_CLOEXEC);
}
} else if (ret == -1) {
if (errno == EINTR)
goto retry;
else if (errno != EAGAIN)
err(1, "pread()");
} else if (ret != 0) {
goto retry;
}
set_async(fd, 0);
fexecve(fd, args, NULL);
err(1, "fexecve()");
}
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