/* teepipe -- tee output to both stdout and a program
 * Copyright (C) 2000 Bruce Guenter <bruceg@em.ca>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include "fork.h"

void err(const char* msg)
{
  write(2, "teepipe: Error: ", 16);
  write(2, msg, strlen(msg));
  write(2, "\n", 1);
  exit(1);
}

void err2(const char* msg1, const char* msg2)
{
  write(2, "teepipe: Error: ", 16);
  write(2, msg1, strlen(msg1));
  write(2, msg2, strlen(msg2));
  write(2, "\n", 1);
  exit(1);
}

#define BUFSIZE 4096

void main_loop(int fd)
{
  for(;;) {
    char buf[BUFSIZE];
    ssize_t rd = read(0, buf, BUFSIZE);
    if(rd == 0 || rd == -1)
      break;
    if(write(fd, buf, rd) != rd)
      err("Error writing to program");
    if(write(1, buf, rd) != rd)
      err("Error writing to standard output");
  }
}

void exec_child(char** argv, int fd[2])
{
  if(close(fd[1]) || close(0) ||
     dup2(fd[0], 0) || close(fd[0]))
    err("Error setting up pipe as standard input");
  if(close(1) || dup2(2, 1) != 1)
    err("Error setting up standard output");
  execvp(argv[0], argv);
  err2("Error executing", argv[0]);
}
  
int main(int argc, char** argv)
{
  int fd[2];
  int status;
  pid_t pid;
  if(argc < 2)
    err("usage: teepipe program [args ...]");
  if(pipe(fd) == -1)
    err("Could not create pipe");
  pid = fork();
  if(pid == -1)
    err("Could not fork");
  if(!pid)
    exec_child(argv+1, fd);
  signal(SIGPIPE, SIG_IGN);
  signal(SIGCHLD, SIG_IGN);
  close(fd[0]);
  main_loop(fd[1]);
  if(close(fd[1]))
    err("Error closing output pipe");
  if(waitpid(pid, &status, 0) != pid)
    err("Error waiting for program to exit");
  return WIFEXITED(status) ? WEXITSTATUS(status) : 255;
}