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Full Discussion: simple fork() problem
Top Forums UNIX for Dummies Questions & Answers simple fork() problem Post 302458467 by malcolmpdx on Friday 1st of October 2010 12:44:23 AM
Old 10-01-2010
use write() instead of printf(). printf() is buffered, and the child has a copy of the buffer so it also will bring "before" and then print after.

changing the first printf to
Code:
 write(1,"Before", 7);

and the second to
Code:
 write(1,"After",5);

will give you the behavior you want.
 

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PTHREAD_ATFORK(3)					   BSD Library Functions Manual 					 PTHREAD_ATFORK(3)

NAME
pthread_atfork -- register handlers to be called before and after fork() SYNOPSIS
#include <pthread.h> int pthread_atfork(void (*prepare)(void), void (*parent)(void), void (*child)(void)); DESCRIPTION
The pthread_atfork() function declares fork handlers to be called before and after fork(2), in the context of the thread that called fork(2). The handlers registered with pthread_atfork() are called at the moments in time described below: prepare Before fork(2) processing commences in the parent process. If more than one prepare handler is registered they will be called in the opposite order they were registered. parent After fork(2) completes in the parent process. If more than one parent handler is registered they will be called in the same order they were registered. child After fork(2) processing completes in the child process. If more than one child handler is registered they will be called in the same order they were registered. If no handling is desired at one or more of these three points, a null pointer may be passed as the corresponding fork handler. Important: only async-signal-safe functions are allowed on the child side of fork(). See sigaction(2) for details. RETURN VALUES
If successful, the pthread_atfork() function will return zero. Otherwise an error number will be returned to indicate the error. ERRORS
The pthread_atfork() function will fail if: [ENOMEM] The system lacked the necessary resources to add another handler to the list. SEE ALSO
fork(2), pthread(3) STANDARDS
The pthread_atfork() conforms to ISO/IEC 9945-1:1996 (``POSIX.1''). BSD
June 21, 2004 BSD
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