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Re: copying files

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On 2012-02-16, JohnF <john@please.see.sig.for.email.com> wrote:
> int	fcopy( char *infile, char *outfile ) {
> FILE    *inptr = fopen(infile,"rb"),	/*open file for binary read*/
> 	*outptr = fopen(outfile,"wb");	/*and write*/
> unsigned char buff[256];		/*block of bytes from infile*/
> int     buflen=255, nread=0,nwrite=0,	/*#bytes we try to read/write*/
> 	nrw = 0;			/*total bytes read/written*/
> if ( inptr!=NULL && outptr!=NULL ) {	/*have opened files*/
>   while ( 1 ) {				/*read & write them till eof*/
>     /* --- read bytes from infile --- */
>     nread = fread(buff,sizeof(unsigned char),buflen,inptr); /*read*/

sizeof(unsigned char) is 1 by definition.
Is there a particular reason why you are reading one byte less than
the size of the buffer? It seems more logical to use the entire buffer:

  nread = fread(buff, 1, sizeof buff, inptr);

>     if ( nread < 1 ) break;		/* no bytes left in file */
>     /* --- write bytes to outfile --- */
>     nwrite = fwrite(buff,sizeof(unsigned char),nread,outptr); /*write*/
>     if ( nwrite != nread ) { nrw=(-1); break; } /*problem writing*/
>     nrw += nwrite;			/*total #bytes*/
>     if ( nread < buflen ) break;	/* no bytes left in file */

  if (nread < sizeof buff) break;

>     } /* --- end-of-while(1) --- */
>   fclose(inptr); fclose(outptr);	/* close files */
>   } /* --- end-of-if(fileptrs!=NULL) --- */
> return ( nrw );				/*back to caller with file size*/

Potential file descriptor leak: if one of the files could be opened
but the other couldn't, the opened file is not closed.
Also, in this case 0 is returned, so from the return value you
cannot distinguish between having fopen errors, and having completed
a successful copy of an empty file.

> } /* --- end-of-function fcopy() --- */
>
> ...which I've snipped from some code that works (with a few
> essentially cosmetic changes so it reads okay as a code fragment).

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copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 01:03 -0800
  Re: copying files Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-16 01:23 -0800
    Re: copying files Keith Thompson <kst-u@mib.org> - 2012-02-16 01:31 -0800
      Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 03:14 -0800
        Re: copying files Keith Thompson <kst-u@mib.org> - 2012-02-16 09:43 -0800
          Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 14:59 -0800
            Re: copying files Keith Thompson <kst-u@mib.org> - 2012-02-16 15:06 -0800
    Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 03:13 -0800
      Re: copying files Keith Thompson <kst-u@mib.org> - 2012-02-16 09:56 -0800
        Re: copying files Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-16 10:11 -0800
          Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 15:11 -0800
            Re: copying files Keith Thompson <kst-u@mib.org> - 2012-02-16 15:21 -0800
              Re: copying files Philip Lantz <prl@canterey.us> - 2012-02-17 09:53 -0800
                Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-18 07:22 -0800
            Re: copying files Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-17 03:36 -0800
              Re: copying files Willem <willem@toad.stack.nl> - 2012-02-17 22:04 +0000
                Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-18 07:28 -0800
                Re: copying files Willem <willem@toad.stack.nl> - 2012-02-18 21:28 +0000
              Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-18 07:19 -0800
        Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 15:02 -0800
  Re: copying files Keith Thompson <kst-u@mib.org> - 2012-02-16 01:34 -0800
    Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 03:27 -0800
      Re: copying files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-16 17:11 +0000
        Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 14:57 -0800
      Re: copying files Keith Thompson <kst-u@mib.org> - 2012-02-16 09:54 -0800
    Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 06:41 -0800
  Re: copying files JohnF <john@please.see.sig.for.email.com> - 2012-02-16 09:49 +0000
    Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 03:10 -0800
      Re: copying files JohnF <john@please.see.sig.for.email.com> - 2012-02-16 11:52 +0000
        Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 06:56 -0800
          Re: copying files David Thompson <dave.thompson2@verizon.net> - 2012-02-24 04:43 -0500
        Re: copying files Ike Naar <ike@iceland.freeshell.org> - 2012-02-16 16:19 +0000
          Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 14:50 -0800
        Re: copying files David Thompson <dave.thompson2@verizon.net> - 2012-02-24 04:43 -0500
  Re: copying files Nobody <nobody@nowhere.com> - 2012-02-16 10:58 +0000
    Re: copying files Keith Thompson <kst-u@mib.org> - 2012-02-16 09:41 -0800
      Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 14:59 -0800
      Re: copying files Nobody <nobody@nowhere.com> - 2012-02-17 06:25 +0000
  Re: copying files Kleuske <kleuske@nowhere.net> - 2012-02-16 11:15 +0000
    Re: copying files Hans Vlems <hvlems@freenet.de> - 2012-02-16 06:45 -0800
    Re: copying files Keith Thompson <kst-u@mib.org> - 2012-02-16 09:49 -0800

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