FileSeek

Set the current file position on a file handle.

Declaration

Source position: filutilh.inc line 274

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.

Errors

On error, -1 is returned.

See also

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.