pipe() and poll() problem in C Post: 302478755

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Top Forums Programming pipe() and poll() problem in C Post 302478755 by blackmamba21 on Wednesday 8th of December 2010 10:34:34 PM

12-08-2010

Registered User

descripteur is descriptor in french its because the parent process is suppose to collect the data from the child and write it in a file specified by descriptor.
I spent all day on this and decide to check the return value fo my dup2 and got an error when redirecting the output of my child process from stdout to the pipe tubeSortie[1].

I try replacing fileno(stdout) with 1 but i keep getting the same error:
Erreur lors du dup stdout Unknown error: 0

Im using mac os x with darwin

check this

Code:

void executerCommande( char *commande[], int descripteur, char* option )
{
	int tubeEntree[2];
	int tubeSortie[2];
	int erreur;
	
	erreur = pipe( tubeEntree );
	if ( erreur == -1 )
	{
		printf( "Erreur lors de la cr�ation du tube %s\n", strerror( errno ) );
		exit( 1 );
	}
	erreur = pipe( tubeSortie );
	if ( erreur == -1 )
	{
		printf( "Erreur lors de la cr�ation du tube %s\n", strerror( errno ) );
		exit( 1 );
	}

	pid_t pid = fork();
	if ( pid == -1 )	// erreur
	{
		perror( "fork a �chou�" );
		exit( 1 );
	}
	else if ( pid == 0 )	// child
	{
		erreur = close( tubeEntree[1] );		// closing writing end of tube from parent to child
		if ( erreur == -1 )
		{
			printf( "Erreur lors du close %s\n", strerror( errno ) );
			exit( 1 );
		}
		erreur = close( tubeSortie[0] );		// closing reading end of tube from child to parent
		if ( erreur == -1 )
		{
			printf( "Erreur lors du close %s\n", strerror( errno ) );
			exit( 1 );
		}
		if ( dup2 ( tubeSortie[1], fileno(stdout) ) == -1 );	// redirecting stdout to writing end of tube from child to parent
		{
			printf( "Erreur lors du dup stdout %s\n", strerror( errno ) );
			exit( 1 );
		}

blackmamba21

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LEARN ABOUT FREEBSD

vfork

VFORK(2)						      BSD System Calls Manual							  VFORK(2)

NAME

     vfork -- create a new process without copying the address space

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

     pid_t
     vfork(void);

DESCRIPTION

     The vfork() system call can be used to create new processes without fully copying the address space of the old process, which is horrendously
     inefficient in a paged environment.  It is useful when the purpose of fork(2) would have been to create a new system context for an
     execve(2).  The vfork() system call differs from fork(2) in that the child borrows the parent's memory and thread of control until a call to
     execve(2) or an exit (either by a call to _exit(2) or abnormally).  The parent process is suspended while the child is using its resources.

     The vfork() system call returns 0 in the child's context and (later) the pid of the child in the parent's context.

     The vfork() system call can normally be used just like fork(2).  It does not work, however, to return while running in the child's context
     from the procedure that called vfork() since the eventual return from vfork() would then return to a no longer existent stack frame.  Be
     careful, also, to call _exit(2) rather than exit(3) if you cannot execve(2), since exit(3) will flush and close standard I/O channels, and
     thereby mess up the parent processes standard I/O data structures.  (Even with fork(2) it is wrong to call exit(3) since buffered data would
     then be flushed twice.)

RETURN VALUES

     Same as for fork(2).

SEE ALSO

     _exit(2), execve(2), fork(2), rfork(2), sigaction(2), wait(2), exit(3)

HISTORY

     The vfork() system call appeared in 2.9BSD.

BUGS

     To avoid a possible deadlock situation, processes that are children in the middle of a vfork() are never sent SIGTTOU or SIGTTIN signals;
     rather, output or ioctl(2) calls are allowed and input attempts result in an end-of-file indication.

BSD
								 November 13, 2009							       BSD

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