minix/commands/nohup/nohup.c

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2009-10-06 16:16:35 +02:00
/*
* Copyright (c) 2009, Erik van der Kouwe
* All rights reserved.
*
* 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. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Functionality implemented according to this specification:
* http://www.opengroup.org/onlinepubs/000095399/utilities/nohup.html
*/
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <unistd.h>
#define NOHUP_OUT_FILENAME "nohup.out"
static void print_usage(const char *argv0)
{
printf("Usage: %s command [arg...]\n", argv0);
}
static int redirect_tty(void)
{
int fd;
char buffer[PATH_MAX + 1], *home;
/* redirect stdout to a file if needed */
if (isatty(STDOUT_FILENO))
{
/* first try: current directory */
fd = open(NOHUP_OUT_FILENAME, O_WRONLY | O_APPEND | O_CREAT, S_IRUSR | S_IWUSR);
if (fd < 0)
{
/* alternative: home directory */
home = getenv("HOME");
if (home)
{
snprintf(buffer, sizeof(buffer), "%s/%s", home, NOHUP_OUT_FILENAME);
buffer[sizeof(buffer) - 1] = 0;
fd = open(buffer, O_WRONLY | O_APPEND | O_CREAT, S_IRUSR | S_IWUSR);
}
}
if (fd < 0)
{
perror("cannot create " NOHUP_OUT_FILENAME " and $HOME/" NOHUP_OUT_FILENAME);
return -1;
}
/* move the fd to stdout */
if (dup2(fd, STDOUT_FILENO) < 0 || close(fd) < 0)
{
perror("cannot redirect stdout");
return -1;
}
}
/* redirect stderr to stdout if needed */
if (isatty(STDERR_FILENO))
{
if (dup2(STDOUT_FILENO, STDERR_FILENO) < 0)
{
perror("cannot redirect stderr");
return -1;
}
}
return 0;
}
int main(int argc, char **argv)
{
struct sigaction sa;
/* check parameters */
if (argc < 2)
{
print_usage(argv[0]);
return 127;
}
/* ignore SIGHUP */
sa.sa_handler = SIG_IGN;
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
if (sigaction(SIGHUP, &sa, NULL) < 0)
{
perror("cannot ignore SIGHUP");
return 127;
}
/* redirect TTY input and output */
if (redirect_tty() < 0)
return 127;
/* run the command */
execvp(argv[1], argv + 1);
perror("cannot execute");
/* exit code depends on whether the utility was found */
switch (errno)
{
case ELOOP:
case ENAMETOOLONG:
case ENOENT:
case ENOTDIR:
/* utility not found */
return 127;
default:
/* exec failed for other reason */
return 126;
}
}