There are many ways to implement these and similar functions. The following example is a great start for a string handling unit add to your programming tool box.

unit StrFunc;
interface
procedure LTrim(var s : string);
procedure RTrim(var s : string);
procedure Trim(var s : string);
implementation
{$R *.DFM}
procedure LTrim(var s : string);
begin
  while ((length(s) > 0) and
         (s[ ] = #32)) do
    Delete(s,  ,  );
end;
procedure RTrim(var s : string);
begin
  while ((length(s) > 0) and
         (s[Length(s)] = #32)) do
    Delete(s, Length(s),  );
end;
procedure Trim(var s : string);
begin
  LTrim(s);
  RTrim(s);
end;
end.