CODEWITHSUNDEEP
c++batch-file
LoukMouk
LoukMouk

Reputation: 512

How to pass parameters and get returned exit value to/from a batch file in c++ windows

CONTEXT :

-Windows 10

-C++

-Batch file

-I want to call a .bat file in a .cpp file and get an int as return value

-The batch file counts and renames .jpg files in a given folder passed as parameter

-Batch file code:

::%1 is the path to the base folder
::%2 is the name of the folder of the images
setlocal enabledelayedexpansion
@echo off

CD /D %1
set cnt=0
for %%f in (%2\*) do (
    set newName=000!cnt!
    set newName=!newname:~-4!
    ren %%f !newName!.jpg
    set /a cnt+=1
)

@echo %cnt% files renamed in order
exit /b %cnt%

QUESTION :

I think I already know how to pass parameters... You need put spaces after the .bat file you call and enter the wanted parameters.

ex:

To run my script in the L:/baseFolder/water folder, I would use :

system(file.bat L:\\baseFolder water)

How do I get the cnt value returned with exit /b %cnt% as a variable in my cpp file?

Am I supposed to use exit to get this integer?

Bonus: What if I want to return multiple values?

Upvotes: 2

Views: 1461

Answers (2)

Scheff's Cat
Scheff's Cat

Reputation: 20141

MSDN describes the usage of system(). I cite the part about return value:

If command is NULL and the command interpreter is found, returns a nonzero value. If the command interpreter is not found, returns 0 and sets errno to ENOENT. If command is not NULL, system returns the value that is returned by the command interpreter. It returns the value 0 only if the command interpreter returns the value 0.

Somehow, I assumed that return code of batch file is the return code of command interpreter but I was not fully sure nor I found an appropriate doc. concerning this.

Thus, I made a little sample and tried it locally.

testExitBat.cc:

#include <Windows.h>
#include <iostream>

int main()
{
  int ret = system("testExitBat.bat Hello");
  std::cout << "testExitBat.bat returned " << ret << '\n';
  return 0;
}

testExitBat.bat:

::%1 an argument
echo "$1: '"%1%"'"
exit /b 123

I compiled and ran it on VS2013 (Windows 10):

C:\Users\Scheff>echo "$1: '"Hello"'"
"$1: '"Hello"'"

C:\Users\Scheff>exit /b 123
testExitBat.bat returned 123

Upvotes: 2

Michael Surette
Michael Surette

Reputation: 711

Both g++ and vs have the filesystem header under experimental, which may be a better solution. If you prefer the environmental variable solution then std::getenv will do that.

It's been a long time since I've done any batch file programming, but I seem to remember that you can set environmental variables in there.

Upvotes: 0

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