FileSeek
Set the current file position on a file handle.
Declaration
Source position: filutilh.inc line 227
function FileSeek(Handle: THandle; FOffset: LongInt; Origin: LongInt)
: LongInt;
function FileSeek(Handle: THandle; FOffset: Int64; Origin: LongInt)
: Int64;
Description
FileSeek sets the file pointer on position Offset, starting from Origin. Origin can be one of the following values:
- fsFromBeginning
- Offset is relative to the first byte of the file. This position is zero-based. i.e. the first byte is at offset 0.
- fsFromCurrent
- Offset is relative to the current position.
- fsFromEnd
- Offset is relative to the end of the file. This means that Offset can only be zero or negative in this case.
If successful, the function returns the new file position, relative to the beginning of the file.
Remark
The above mentioned constants do not exist in Delphi. !!!
Errors
On error, -1 is returned.
See also
| Name | Description |
|---|---|
| FileClose | Close a file handle. |
| FileCreate | Create a new file and return a handle to it. |
| FileOpen | Open an existing file and return a file handle |
| FileRead | Read data from a file handle in a buffer. |
| FileTruncate | Truncate an open file to a given size. |
| FileWrite | Write data from a buffer to a given file handle. |
Example
Program Example37;
{ This program demonstrates the FileCreate/FileSeek/FileReed/FileTruncate functions }
Uses sysutils;
Var I,J,F : Longint;
Begin
F:=FileCreate ('test.dat');
If F=-1 then
Halt(1);
For I:=0 to 100 do
FileWrite(F,I,SizeOf(i));
FileClose(f);
F:=FileOpen ('test.dat',fmOpenRead);
For I:=0 to 100 do
begin
FileRead (F,J,SizeOF(J));
If J<>I then
Writeln ('Mismatch at file position ',I)
end;
FileSeek(F,0,fsFromBeginning);
Randomize;
Repeat
FileSeek(F,Random(100)*4,fsFromBeginning);
FileRead (F,J,SizeOf(J));
Writeln ('Random read : ',j);
Until J>80;
FileClose(F);
F:=FileOpen('test.dat',fmOpenWrite);
I:=50*SizeOf(Longint);
If FileTruncate(F,I) then
Writeln('SuccessFully truncated file to ',I,' bytes.');
FileClose(F);
End.