Extract string from a text file using 2 delimiters - string

Question

I'm trying to extract a string from a text file using 2 delimiters. One to start and one to stop.
Example:
Hi my name is$John and I'm happy/today
What I need to do is to call a function that would return the string between $ and /. I've been looking everywhere but I can't seem to find something useful and I'm new to programming.

Answer 1

The above functions won't work if the 2nd text is also appearing before the 1st pattern...
You should use PosEx() instead of Pos():
You can do it with Pos and Copy:
function ExtractText(const Str: string; const Delim1, Delim2: string): string;
var
pos1, pos2: integer;
begin
result := '';
pos1 := Pos(Delim1, Str);
if pos1 > 0 then begin
pos2 := PosEx(Delim2, Str, pos1+1);
if pos2 > 0 then
result := Copy(Str, pos1 + 1, pos2 - pos1 - 1);
end;
end;

Answer 2

You can do it with Pos and Copy:
function ExtractText(const Str: string; const Delim1, Delim2: char): string;
var
pos1, pos2: integer;
begin
result := '';
pos1 := Pos(Delim1, Str);
pos2 := Pos(Delim2, Str);
if (pos1 > 0) and (pos2 > pos1) then
result := Copy(Str, pos1 + 1, pos2 - pos1 - 1);
end;

Answer 3

I'd do it something like this:
function ExtractDelimitedString(const s: string): string;
var
p1, p2: Integer;
begin
p1 := Pos('$', s);
p2 := Pos('/', s);
if (p1<>0) and (p2<>0) and (p2>p1) then begin
Result := Copy(s, p1+1, p2-p1-1);
end else begin
Result := '';//delimiters not found, or in the wrong order; raise error perhaps
end;
end;

Answer 4

Get em all
function ExtractText(const Str: string; const Delim1, Delim2: string): TStringList;
var
c,pos1, pos2: integer;
begin
result:=TStringList.Create;
c:=1;
pos1:=1;
while pos1>0 do
begin
pos1 := PosEx(Delim1, Str,c);
if pos1 > 0 then begin
pos2 := PosEx(Delim2, Str, pos1+1);
if pos2 > 0 then
result.Add(Copy(Str, pos1 + length(delim1), pos2 - (length(delim1) + pos1)));
c:=pos1+1;
end;
end;
end;

Answer 5

Gab, you can write a function to do this using a TFileStream class, and the Copy and Pos functions.
see this sample :
uses
Classes,
SysUtils;
function ExtractString(Const FileName: TFileName;Const IDel,FDel : AnsiString) : AnsiString;
Var
FileStream : TFileStream;
i,f : Integer;
begin
FileStream:= TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite); //oopen the file
try
try
SetLength(Result, FileStream.Size); //set the size of the string
FileStream.Read(Pointer(Result)^, FileStream.Size);//read the content into a string
i:=Pos(IDel,Result);//search the initial delimiter
f:=Pos(FDel,Result);//search the final delimiter
Result:=Copy(Result,i+1,f-i-1); //extract the value between the delimiters
except
Result := '';
raise;
end;
finally
FileStream.Free;
end;
end;
and use in this way
ExtractString('your_file_name','$','/');

Answer 6

In the newer Delphi's you can do it like this.. (yay)
program Project40; {$APPTYPE CONSOLE}
uses RegularExpressions;
const
str = 'Is$John and I''m happy/today';
function GetStr(const aStr: string): string;
begin
Result := TRegEx.Match(aStr, '\$.*/').Value;
Result := Copy(Result, 2, Length(Result) - 2);
end;
begin
Writeln(GetStr(str));
ReadLn;
end.

Answer 7

Assuming both delimiters are single characters as per your post:
function ExtractDelimitedValueFromFile(const aFilename: String;
const aOpenDelim: Char;
const aCloseDelim: Char;
var aValue: String): Boolean;
var
i: Integer;
strm: TStringStream;
delimStart: Integer;
delimEnd: Integer;
begin
result := FALSE;
aValue := '';
delimStart := -1;
delimEnd := -1;
strm := TStringStream.Create;
try
strm.LoadFromFile(aFileName);
for i := 1 to strm.Size do
begin
if (delimStart = -1) and (strm.DataString[i] = aOpenDelim) then
delimStart := i
else if (delimStart <> -1) and (strm.DataString[i] = aCloseDelim) then
delimEnd := i;
result := (delimStart <> -1) and (delimEnd <> -1);
if result then
begin
aValue := Copy(strm.DataString, delimStart + 1, delimEnd - delimStart - 1);
BREAK;
end;
end;
finally
strm.Free;
end;
end;
Usage:
var
str: String;
begin
if ExtractDelimitedValueFromFile('path\filename.ext', '$', '/', str) then
// work with str
else
// delimited value not found in file
end;