Using windows command line from Pascal
- by Jordan
I'm trying to use some windows command line tools from within a short Pascal program. To make it easier, I'm writing a function called DoShell which takes a command line string as an argument and returns a record type called ShellResult, with one field for the process's exitcode and one field for the process's output text.
I'm having major problems with some standard library functions not working as expected. The DOS Exec() function is not actually carrying out the command i pass to it. The Reset() procedure gives me a runtime error RunError(2) unless i set the compiler mode {I-}. In that case i get no runtime error, but the Readln() functions that i use on that file afterwards don't actually read anything, and furthermore the Writeln() functions used after that point in the code execution do nothing as well.
Here's the source code of my program so far. I'm using Lazarus 0.9.28.2 beta, with Free Pascal Compiler 2.24
program project1;
{$mode objfpc}{$H+}
uses
Classes, SysUtils, StrUtils, Dos
{ you can add units after this };
{$IFDEF WINDOWS}{$R project1.rc}{$ENDIF}
type
ShellResult = record
output : AnsiString;
exitcode : Integer;
end;
function DoShell(command: AnsiString): ShellResult;
var
exitcode: Integer;
output: AnsiString;
exepath: AnsiString;
exeargs: AnsiString;
splitat: Integer;
F: Text;
readbuffer: AnsiString;
begin
//Initialize variables
exitcode := 0;
output := '';
exepath := '';
exeargs := '';
splitat := 0;
readbuffer := '';
Result.exitcode := 0;
Result.output := '';
//Split command for processing
splitat := NPos(' ', command, 1);
exepath := Copy(command, 1, Pred(splitat));
exeargs := Copy(command, Succ(splitat), Length(command));
//Run command and put output in temporary file
Exec(FExpand(exepath), exeargs + ' __output');
exitcode := DosExitCode();
//Get output from file
Assign(F, '__output');
Reset(F);
Repeat
Readln(F, readbuffer);
output := output + readbuffer;
readbuffer := '';
Until Eof(F);
//Set Result
Result.exitcode := exitcode;
Result.output := output;
end;
var
I : AnsiString;
R : ShellResult;
begin
Writeln('Enter a command line to run.');
Readln(I);
R := DoShell(I);
Writeln('Command Exit Code:');
Writeln(R.exitcode);
Writeln('Command Output:');
Writeln(R.output);
end.
