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From: andrewsr@acdc.rutgers.edu (Richard L Andrews)
Newsgroups: comp.unix.questions
Subject: fork() and redirection
Message-ID: <Feb.15.14.14.27.1990.4568@acdc.rutgers.edu>
Date: 15 Feb 90 19:14:32 GMT
References: <7638@tank.uchicago.edu> <12137@smoke.BRL.MIL>
Organization: Rutgers Univ., New Brunswick, N.J.
Lines: 52

Why does the fork command start the child process at the point where
it occurs in the program normally, yet restart the child process when
the output is redireced to a file?  (I am using the tsch shell on UNIX).

Example:
--------
Code:
-----
#include <stdio.h>

main(

     printf("This is a test.\n");
     printf("Statement 2 in main.\n");
     if (fork() == 0) {
          printf("Child statement 1\n");
          printf("Child statement 2\n");
     } else {
          printf("Parent statement 3\n");
          printf("Parent statement 4\n");
     }
}

when output to terminal:
------------------------
This is a test.
Statement 2 in main.
Parent statement 3
Parent statement 4
Child statement 1
Child statement 2

When piped to a file, the file reads:
-------------------------------------
This is a test.
Statement 2 in main.
Parent statement 3
Parent statement 4
This is a test.
Statement 2 in main.
Child statement 1
Child statement 2


When displayed on the terminal, although the output can be
undetermined, it never prints "This is a test." twice.

Much thanks in advance.
-Rich
-- 
  //   Richard L Andrews II   |"Like any good philosophical discussion, the
\X/ andrewsr@topaz.rutgers.edu| conclusion is left unresolved." -McLaughlin