Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!cec2!news
From: flan@cics.Berkeley.EDU (Ian Flanigan)
Newsgroups: comp.unix.questions
Subject: Odd ouput redirection in background script
Keywords: Odd, strange, wierd, csh, shell, background, script
Message-ID: <1991Feb4.211315.13175@cec1.wustl.edu>
Date: 4 Feb 91 21:13:15 GMT
Sender: news@cec1.wustl.edu (USENET News System)
Reply-To: flan@cics.Berkeley.EDU (Ian Flanigan)
Organization: Center for Intelligent Computing Systems
Lines: 59


Today I was cooking up a small program to save me the trouble of having to
wait for my rsh's to finish:

/* Background Processes */
#include <stdio.h>

main(argc, argv)
int argc;
char *argv[];
{
  if (fork()) 
      exit(0);
  execvp(argv[0],&argv[1]);
  printf("OOps\n");
}

I used the following script to give it a test:

#!/bin/csh

ls > /tmp/tt$$

Then I typed, "background test_scr" to give it a test and it worked fine;
I got the output in the file in /tmp and everything.  I then tried to use
it with rsh and it was a complete failure.  Right away I remebered that
the child process inherits everything, so I needed to close stdin and
stdout.  So the program became:

/* Background Processes */
#include <stdio.h>

main(argc, argv)
int argc;
char *argv[];
{
  if (fork()) 
    exit(0);
  close(0);
  close(1);
  execvp(argv[0],&argv[1]);
  printf("OOps\n");
}

Easy.  Now I gave it a test with, "background test_scr" and it wrote the
directory listing to my screen.  My question: Why?  Not only did I close
stdout, but I also had it re-directed in the script.  Is it a probelem
with the shell?

I've gotten the program to work the way I want it to, now, but I am
baffled by the odd behavior.

Thanks for any info.

-- 
Ian Flanigan

flan@cics.wustl.edu              "You can never have too many napkins."
wucs1.wustl.edu!cics!flan@uucp