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Full Discussion: read and write stdin/stdout in unix
Top Forums Programming read and write stdin/stdout in unix Post 302414793 by MrUser on Wednesday 21st of April 2010 03:31:08 AM
Old 04-21-2010
read and write stdin/stdout in unix
Hi,
i am using the below program to read from the standard input or to write to standard out put.

i know that using highlevel functions this can be done better than what i have done here.

i just want to know is there any other method by which i find the exact number of characters ( this will vary in each iteration ) , and write that to STDOUT.

this process i want to terminate with a press of "q".

does read syscall stores the null at the end of string, i have not found that in debug mode.

below is the sample code but its has got the problem of reading and writing garbages.


Code:
#include<unistd.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include <stdio.h>
#include<string.h>

int main( void )
{
        char buf[20];

        while( 1 )
        {
                       read(STDIN_FILENO , buf ,  sizeof( buf ));
                       write(STDOUT_FILENO, buf , strlen( buf ));

                if(!strcmp(buf,"q\n"))
                        break;
        }

        return 0;
}

 

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LEARN ABOUT CENTOS

gsm

GSM(3)							     Library Functions Manual							    GSM(3)

NAME

       gsm_create, gsm_destroy, gsm_encode, gsm_decode -- GSM 06.10 lossy sound compression

SYNOPSIS

       #include "gsm.h"

       gsm gsm_create();

       void gsm_encode(handle, src, dst)
       gsm handle;
       gsm_signal src[160];
       gsm_frame dst;

       int gsm_decode(handle, src, dst)
       gsm handle;
       gsm_frame src;
       gsm_signal dst[160];

       void gsm_destroy(handle)
       gsm handle;

DESCRIPTION

       Gsm is an implementation of the final draft GSM 06.10 standard for full-rate speech transcoding.

       gsm_create()  initializes  a  gsm  pass	and  returns  a  'gsm'	object	which can be used as a handle in subsequent calls to gsm_decode(),
       gsm_encode() or gsm_destroy().

       gsm_encode() encodes an array of 160 13-bit samples (given as gsm_signal's, signed integral values of at least 16 bits) into a gsm_frame of
       33 bytes.  (gsm_frame is a type defined as an array of 33 gsm_bytes in gsm.h.)

       gsm_decode()  decodes  a  gsm_frame  into an array of 160 13-bit samples (given as gsm_signals), which sound rather like what you handed to
       gsm_encode() on the other side of the wire.

       gsm_destroy() finishes a gsm pass and frees all storage associated with it.

   Sample format
       The following scaling is assumed for input to the algorithm:
	  0  1				   11 12
	  S..v..v..v..v..v..v..v..v..v..v..v..v..*..*..*
       Only the top 13 bits are used as a signed input value.
       The output of gsm_decode() has the three lower bits set to zero.

RETURN VALUE

       gsm_create() returns an opaque handle object of type gsm, or 0 on error.  gsm_decode() returns -1 if the passed frame is invalid, else 0.

EXAMPLE

       #include "gsm.h"

       gsm handle;
       gsm_frame buf;
       gsm_signal sample[160];
       int cc, soundfd;

       play() {  /* read compressed data from standard input, write to soundfd */

	    if (!(handle = gsm_create())) error...
	    while (cc = read(0, (char *)buf, sizeof buf)) {
		 if (cc != sizeof buf) error...
		 if (gsm_decode(handle, buf, sample) < 0) error...
		 if (write(soundfd, sample, sizeof sample) != sizeof sample)
		      error...
	    }
	    gsm_destroy(handle);
       }

       record() {     /* read from soundfd, write compressed to standard output */

	    if (!(handle = gsm_create())) error...
	    while (cc = read(soundfd, sample, sizeof sample)) {
		 if (cc != sizeof sample) error...
		 gsm_encode(handle, sample, buf);
		 if (write(1, (char *)buf, sizeof buf) != sizeof sample)
		      error...
	    }
	    gsm_destroy(handle);
       }

BUGS

       Please direct bug reports to jutta@cs.tu-berlin.de and cabo@cs.tu-berlin.de.

SEE ALSO

       toast(1), gsm_print(3), gsm_explode(3), gsm_option(3)

																	    GSM(3)
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