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/* runpty.c - Run a process under a pseudo-tty
*
* This code is Copyright (c) 2017, by the authors of nmh. See the
* COPYRIGHT file in the root directory of the nmh distribution for
* complete copyright information.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <fcntl.h>
#include <termios.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/select.h>
#include <time.h>
#include <errno.h>
#define COMMAND_TIMEOUT 30
static void run_command(char *argv[], int master_in, int master_out);
static int open_master_pty(const char *desc);
static void die(const char *fmt, ...)
#if __GNUC__ > 2
__attribute__((__noreturn__))
#endif
#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
__attribute__((format(printf, 1, 2)))
#endif
;
int
main(int argc, char *argv[])
{
int master_in, master_out, cc, status;
time_t starttime, now;
pid_t child;
unsigned char readbuf[1024];
FILE *output;
if (argc < 3) {
die("%s: too few arguments\n"
"usage: %s output-filename command [arguments...]\n",
*argv, *argv);
}
master_in = open_master_pty("input");
master_out = open_master_pty("output");
if ((child = fork()) == -1) {
die("fork() failed: %s\n", strerror(errno));
}
if (child == 0) {
run_command(argv + 2, master_in, master_out); /* Does not return. */
}
if (!(output = fopen(argv[1], "w"))) {
die("Unable to open \"%s\" for output: %s\n", argv[1],
strerror(errno));
}
starttime = time(NULL);
for (;;) {
fd_set readfds;
struct timeval tv;
FD_ZERO(&readfds);
FD_SET(master_out, &readfds);
/*
* After we get our first bit of data, close the master pty
* connected to standard input on our slave; that will generate
* an EOF.
*/
tv.tv_sec = starttime + COMMAND_TIMEOUT - time(NULL);
if (tv.tv_sec < 0)
tv.tv_sec = 0;
tv.tv_usec = 0;
cc = select(master_out + 1, &readfds, NULL, NULL, &tv);
if (cc < 0) {
die("select() failed: %s\n", strerror(errno));
}
if (cc > 0 && FD_ISSET(master_out, &readfds)) {
cc = read(master_out, readbuf, sizeof(readbuf));
if (cc <= 0)
break;
fwrite(readbuf, 1, cc, output);
if (master_in != -1) {
close(master_in);
master_in = -1;
}
}
now = time(NULL);
if (now >= starttime + COMMAND_TIMEOUT) {
fprintf(stderr, "Command execution timed out: %ld to %ld: %d\n",
starttime, now, cc);
break;
}
}
if (master_in != -1)
close(master_in);
close(master_out);
fclose(output);
waitpid(child, &status, 0);
exit(0);
}
static void
run_command(char *argv[], int master_in, int master_out)
{
const char *slavename;
int slave;
/* Open the two slave pseudo-ttys and close the masters after we are
* done with them. */
if (!(slavename = ptsname(master_in))) {
die("Unable to determine name of slave pty: %s\n",
strerror(errno));
}
if ((slave = open(slavename, O_RDWR)) == -1) {
die("Unable to open slave pty \"%s\": %s\n", slavename,
strerror(errno));
}
dup2(slave, STDIN_FILENO);
close(slave);
close(master_in);
if (!(slavename = ptsname(master_out))) {
die("Unable to determine name of slave pty: %s\n",
strerror(errno));
}
if ((slave = open(slavename, O_RDWR | O_NOCTTY)) < 0) {
die("Unable to open slave pty \"%s\": %s\n", slavename,
strerror(errno));
}
dup2(slave, STDOUT_FILENO);
dup2(slave, STDERR_FILENO);
close(slave);
close(master_out);
execvp(*argv, argv);
die("execvp(%s) failed: %s\n", *argv, strerror(errno));
}
static int
open_master_pty(const char *desc)
{
int fd;
if ((fd = posix_openpt(O_RDWR | O_NOCTTY)) == -1) {
die("Unable to open master %s pseudo-tty: %s\n", desc, strerror(errno));
}
if (grantpt(fd) == -1) {
die("Unable to grant permissions to master %s pty: %s\n", desc,
strerror(errno));
}
if (unlockpt(fd) == -1) {
die("Unable to unlock master %s pty: %s\n", desc, strerror(errno));
}
return fd;
}
static void
die(const char *fmt, ...)
{
va_list args;
va_start(args, fmt);
vfprintf(stderr, fmt, args);
va_end(args);
exit(1);
}
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