From:	an118 AT chebucto DOT ns DOT ca (Graham Howard Wile)
Newsgroups:	comp.os.msdos.djgpp
Subject:	NEED HELP with "_read()"
Date:	7 Dec 1996 22:20:31 GMT
Organization:	Chebucto Community Net
Lines:	59
Message-ID:	<58cqjf$6ie@News.Dal.Ca>
NNTP-Posting-Host:	chebucto.ns.ca
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

	In the "libc" documentation file, it tells how to use "_read()"
by showing that you need to feed it these parameters:


			ssize_t _read(int fildes, void *buf, size_t nbyte);

	The parameter I am having trouble with is the "int fildes". In 
the example in the file "libc" they write:

			int r = read(0, buf, 10);

	I notice they use a "0" for the file description number. Are you 
always suppossed to use 0? If not, how do you know what number represents 
the file you just opened with "fopen"?

	Below is some code I work which compiles great, but locks up on 
the line:

			bytes_read = _read(0, read_into_buffer, 10);

	Here is my code:

			
			#include <fstream.h> 
			#include <io.h> 
			#include <stdio.h> 

			void main()
			  {
			  char read_into_buffer[60]; 
     			  int bytes_read, file_number; 

     			  FILE *f = fopen("testing.txt", "rt"); 

     			  cout << "Pointer: " << f << endl; 

     			  bytes_read = _read(0, read_into_buffer, 10); 

     			  fclose(f);
			  }

     
	The file opens well, and the "cout << "Pointer: " << f << endl;" 
even returns a valid non-zero address to my file object.

	But it hangs and doesn't return a value for the number of bytes read 
at the line:

			bytes_read = _read(0, read_into_buffer, 10);

	I'm assuming the parameter 0 isn't the right one for the opened 
file "testing.txt", as since I am in windows, a lot of other files are 
open at this time as well. If I am right, how does one determine the 
correct number to enter for this parameter ?

					Thank-you
						Graham H. W.

		

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