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<TITLE>Int 21/AH=42h
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Int 21/AH=42h - DOS 2+ - LSEEK - SET CURRENT FILE POSITION -
AH = 42h
AL = origin of move
00h start of file
01h current file position
02h end of file
BX = file handle
CX:DX = (signed) offset from origin of new file position
Return: CF clear if successful
DX:AX = new file position in bytes from start of file
CF set on error
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<h2>Int 21/AH=42h
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<h3><font color=#C00040>DOS 2+ - LSEEK - SET CURRENT FILE POSITION</font></h3>
<PRE>
AH = 42h
AL = origin of move
00h start of file
01h current file position
02h end of file
BX = file handle
CX:DX = (signed) offset from origin of new file position<br>
<p><b>Return:</b><br>CF clear if successful
DX:AX = new file position in bytes from start of file
CF set on error
AX = error code (01h,06h) <a href="javascript:if(confirm('http://www.ctyme.com/intr/rb-0000.htm \n\nThis file was not retrieved by Teleport Pro, because it was unavailable, or its retrieval was aborted, or the project was stopped too soon. \n\nDo you want to open it from the server?'))window.location='http://www.ctyme.com/intr/rb-0000.htm#Table0'" tppabs="http://www.ctyme.com/intr/rb-0000.htm#Table0"></a>(see #01680 at AH=59h/BX=0000h)
</PRE>
<p><b>Notes:</b>
For origins 01h and 02h, the pointer may be positioned before the
start of the file; no error is returned in that case (except under
Windows NT), but subsequent attempts at I/O will produce errors.
If the new position is beyond the current end of file, the file will
be extended by the next write (see AH=40h); for FAT32 drives, the
file must have been opened with AX=6C00h with the "extended size"
flag in order to expand the file beyond 2GB
<p><b>BUG:</b>
Using this method to grow a file from zero bytes to a very large size
can corrupt the FAT in some versions of DOS; the file should first
be grown from zero to one byte and then to the desired large size
<p><b>See Also:</b>
<a href="rb-2601.htm" tppabs="http://www.ctyme.com/intr/rb-2601.htm">AH=24h</a> - <a href="rb-4408.htm" tppabs="http://www.ctyme.com/intr/rb-4408.htm">INT 2F/AX=1228h</a>
<p>
<b>Category: <a href="cat-010.htm" tppabs="http://www.ctyme.com/intr/cat-010.htm">
DOS Kernel</a>
- <a href="int-21.htm" tppabs="http://www.ctyme.com/intr/int-21.htm">
Int 21h</a>
- <a href="alpha-d.htm" tppabs="http://www.ctyme.com/intr/alpha-d.htm">
D</a>
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