/* $Id: dlnohup.c 34 2007-09-19 12:54:18Z dleigh $
 *
 * dlnohup.c - nohup replacement with control over stdin, stdout, stderr
 *
 * Usage: dlnohup <in.file> <out.file> <err.file> <program> [<args> ...]
 *
 * - The files for the 3 streams are required (use /dev/null if you want to
 *   ignore that stream).
 * 
 * - Files for stdout and stderr output will be created if they do not exist
 *   (the program will abort if the stdin file does not exist).
 *
 * - If they do exist, the output files will be appended to, not truncated;
 *   note that this may CORRUPT files mounted over NFS if multiple programs
 *   are appending to the same file.

 -----

 Copyright (c) 2006 Dylan Leigh.


 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:

 1. Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.

 2. Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.

 3. Modified versions must be plainly marked as such, and must not be
    misrepresented as being the original software.

 4. The names of the authors or copyright holders must not be used to
    endorse or promote products derived from this software without prior
    written permission.


 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.

 IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE, EVEN IF ADVISED
 OF THE POSSIBILITY OF SUCH DAMAGE.
 
 -----

 */

#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/stat.h>

int main(int argc, char **argv)
{
	int infd, outfd, errfd;

	//check usage
	if (argc < 5)
	{
		fprintf(stderr, 
"Usage: %s <in.file> <out.file> <err.file> <program> [<args>...]\n", argv[0]);
		return EXIT_FAILURE;
		/* Note: return is used when no special cleanup is desired. exit()
		 * should close open files according to ANSI C; returningfrom main()
		 * makes no such guarantee. */
	}
	
	//disconnect sighup
	if (signal(SIGHUP, SIG_IGN) == SIG_ERR)
	{
		fprintf(stderr, "%s: signal() error\n", argv[0]);
		exit(EXIT_FAILURE);
	}

	//open files
	infd = open(argv[1], O_RDONLY);
	if (infd == -1)
	{
		perror(argv[1]);
		exit(EXIT_FAILURE);
	}
	outfd = open(argv[2],
				 O_WRONLY | O_CREAT | O_APPEND,
				 S_IRUSR | S_IWUSR | S_IRGRP);
	if (outfd == -1)
	{
		perror(argv[2]);
		exit(EXIT_FAILURE);
	}
	errfd = open(argv[3],
				 O_WRONLY | O_CREAT | O_APPEND,
				 S_IRUSR | S_IWUSR | S_IRGRP);
	if (errfd == -1)
	{
		perror(argv[3]);
		exit(EXIT_FAILURE);
	}

	//connect files
	if (dup2(infd, STDIN_FILENO) == -1)
	{
		perror(argv[0]);
		exit(EXIT_FAILURE);
	}
	if (dup2(outfd, STDOUT_FILENO) == -1)
	{
		perror(argv[0]);
		exit(EXIT_FAILURE);
	}
	if (dup2(errfd, STDERR_FILENO) == -1)
	{
		perror(argv[0]);
		exit(EXIT_FAILURE);
	}
	close(infd);
	close(outfd);
	close(errfd);

	//exec
	execvp(argv[4], &argv[4]);
	
	//on error print to stderr TODO print to original stderr?
	fprintf(stderr, "%s: execvp error: ", argv[0]);
	perror(NULL);
	exit(EXIT_FAILURE);

	return EXIT_FAILURE;
}