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Full Discussion: share file descriptor between childs
Top Forums Programming share file descriptor between childs Post 302245575 by redoubtable on Friday 10th of October 2008 11:26:48 AM
Old 10-10-2008
The code you posted has a problem. But even if you solve that problem, there is another one. fork() dup()licates fd's from the parent but if you don't have some kind of synchronous read between the childs, you'll have unexpected results.

Do you really want to use multiple processes to read the same fd?

Try running this several times to see what I'm talking about:
Code:
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#define CHILDS_N 5

void worker(int * fd)
{
        char buf[20];

        memset (buf, 0x0, sizeof (buf));
        read(*fd, buf, sizeof (buf)-1);
        printf ("%s\n", buf);

}


int
main ()
{
        pid_t childs[CHILDS_N];
        int fd;
        int i;
        fd = open ("Client_Files.txt", O_RDONLY);
        if (fd == -1)
                exit(1);


        for (i=0; i < CHILDS_N; i++)
        {
                childs[i] = fork();
                if (childs[i] == 0)
                {
                        worker(&fd);
                }
                else
                {
//                      printf ("parent: %d\n", getpid());
                }
        }
}

 

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LEARN ABOUT CENTOS

paps

PAPS(1) 						      General Commands Manual							   PAPS(1)

NAME

       paps - UTF-8 to PostScript converter using Pango

SYNOPSIS

       paps [options] files...

DESCRIPTION

       paps reads a UTF-8 encoded file and generates a PostScript language rendering of the file. The rendering is done by creating outline curves
       through the pango ft2 backend.

OPTIONS

       These programs follow the usual GNU command line syntax, with long options starting with  two  dashes  (`-').   A  summary  of  options	is
       included below.

       --landscape
	      Landscape output. Default is portrait.

       --columns=cl
	      Number of columns output. Default is 1.

       --font=desc
	      Set the font description. Default is Monospace 12.

       --rtl  Do rtl layout.

       --paper ps
	      Choose paper size. Known paper sizes are legal, letter, a4. Default is A4.

       --bottom-margin=bm
	      Set bottom margin in postscript points (1/72 inch). Default is 36.

       --top-margin=tm
	      Set top margin. Default is 36.

       --left-margin=lm
	      Set left margin. Default is 36.

       --right-margin=rm
	      Set right margin. Default is 36.

       --help Show summary of options.

       --header
	      Draw page header for each page.

       --markup
	      Interpret the text as pango markup.

       --encoding=ENCODING
	      Assume the documentation encoding is ENCODING.

       --lpi  Set the lines per inch. This determines the line spacing.

       --cpi  Set the characters per inch. This is an alternative method of specifying the font size.

       --stretch-chars
	      Indicates  that  characters  should be stretched in the y-direction to fill up their vertical space. This is similar to the texttops
	      behaviour.

AUTHOR

       paps was written by Dov Grobgeld <dov.grobgeld@gmail.com>.

       This manual page was written by Lior Kaplan <kaplan@debian.org>, for the Debian project (but may be used by others).

								  April  17, 2006							   PAPS(1)
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