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Date: Wed, 30 Aug 2000 02:48:07 +0900 (JST)
From: Tatsuya Kudoh <cdr@cosmonet.org>
To: FreeBSD-gnats-submit@freebsd.org
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Subject: i386/20925: doscmd(1) does not truncate a file
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>Number:         20925
>Category:       i386
>Synopsis:       doscmd(1) does not truncate a file int write functio-call.
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Aug 29 11:00:01 PDT 2000
>Closed-Date:
>Last-Modified:
>Originator:     Tatsuya Kudoh
>Release:        FreeBSD 3.5-RELEASE i386
>Organization:
>Environment:

	FreeBSD 3.2 or later
	kernel compiled with 'options "VM86"'

>Description:

	Under MS-DOS, the write function-call with size parameter is 0,
	it means file truncating.
	This function is not implemented in doscmd(1).

>How-To-Repeat:

	Some MS-DOS applications. In my environment, LSI Japans's
	LSI C-86 C compiler does not work.

>Fix:

	This is a patch for dsmcd(1) on 3.5-RELEASE
	-------------------------------------------

*** dos.c.old	Sat Aug 12 22:36:06 2000
--- dos.c	Sat Aug 12 22:42:08 2000
***************
*** 1308,1313 ****
--- 1308,1329 ----
  ** write
  */
  static int
+ write_or_truncate(int fd, char *addr, int len)
+ {
+     off_t offset;
+ 
+     if ( len == 0 ){
+ 	offset = lseek(fd,0,SEEK_CUR);
+ 	if( offset < 0 )
+ 	    return -1;
+ 	else
+ 	    return ftruncate(fd,offset);
+     } else {
+ 	return write(fd,addr,len);
+     }
+ }
+ 
+ static int
  int21_40(regcontext_t *REGS)
  {
      char	*addr;
***************
*** 1321,1327 ****
      switch (R_BX) {
      case 0:
  	if (redirect0) {
! 	    n = write (R_BX, addr, nbytes);
  	    break;
  	}
  	n = nbytes;
--- 1337,1343 ----
      switch (R_BX) {
      case 0:
  	if (redirect0) {
! 	    n = write_or_truncate (R_BX, addr, nbytes);
  	    break;
  	}
  	n = nbytes;
***************
*** 1330,1336 ****
  	break;
      case 1:
  	if (redirect1) {
! 	    n = write (R_BX, addr, nbytes);
  	    break;
  	}
  	n = nbytes;
--- 1346,1352 ----
  	break;
      case 1:
  	if (redirect1) {
! 	    n = write_or_truncate (R_BX, addr, nbytes);
  	    break;
  	}
  	n = nbytes;
***************
*** 1339,1345 ****
  	break;
      case 2:
  	if (redirect2) {
! 	    n = write (R_BX, addr, nbytes);
  	    break;
  	}
  	n = nbytes;
--- 1355,1361 ----
  	break;
      case 2:
  	if (redirect2) {
! 	    n = write_or_truncate (R_BX, addr, nbytes);
  	    break;
  	}
  	n = nbytes;
***************
*** 1347,1353 ****
  	    tty_write(*addr++, -1);
  	break;
      default:
! 	n = write (R_BX, addr, nbytes);
  	break;
      }
      if (n < 0)
--- 1363,1369 ----
  	    tty_write(*addr++, -1);
  	break;
      default:
! 	n = write_or_truncate (R_BX, addr, nbytes);
  	break;
      }
      if (n < 0)

>Release-Note:
>Audit-Trail:
>Unformatted:


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