Return value of a function to a function in batch script

Question

This could possibly a duplicate of several questions out there in the SO, dostips and ss64. The research I've done point me to look out for _scope_ in functions. but my solutions is simple and straight forward but still problem exists

what is really behind the SETLOCAL and ENDLOCAL
How contextworkd in batch scripts ex (goto) 2>nul
Why (goto) wrapped in braces (explained in dostips)

Here is the code i've written so far to copy file from one place to another. My Goals were:

Research the scope and contextof batch script
code reuse

    @echo off
    setlocal EnableDelayedExpansion
    goto :main

:main
    setlocal
    set _app=test
    set _base=C:/wamp64/www
    set _destination=!_base!/test
    set _source=%~dp0%/build
    set /A _flag=0

    echo *********************************************
    echo    Deploying in %~1 mode: %TIME%
    echo        Deploy path: !^_destination!
    echo *********************************************

    call :check !_base!, !_app!, _flag
    if !_flag!==0 (
        call :create !_base!, !_app!
    )
    xcopy "!_source!" "!_destination!" /D /C
    exit /b 0
    endlocal

:setbase 
    echo ::::: setting up base :::::
    chdir /D C:

    rem the base dir for app to exists=> %1
    chdir %~1 
    exit /b 0

:check 
    echo ::::: checking for local web server destination :::::
    call :setbase %~1

    set %~3= dir /p|find /C "%~2"
    exit /b 0

:create 
    echo ::::: creating the app folders :::::

    rem setting the base to create app folder %1
    call :setbase %~1
    mkdir %~2
    exit /b 0

endlocal

This is the output i get when i initiate deploy.bat

*********************************************
   Deploying in production mode: 19:28:53.13
       Deploy path: C:/wamp64/www/test
*********************************************
::::: checking for local web server destination :::::
::::: setting up base :::::
0
::::: creating the app folders :::::
::::: setting up base :::::
A subdirectory or file test already exists.

seems like the If !_flag!==0 which is checking whether the app folder exist in the server root and is not working at all. When i learnt the way to pass parameters to other functions; i thought it as passing a pointer like reference but it looks like it is deeply tied to scope. So what's going on here in the code.

In :check, you are aren't actually running the command when you set _flag, you're setting that variable to the literal string. Use for /F to store command output in a variable. — SomethingDark
– SomethingDark, Commented Dec 20, 2018 at 14:54

mojo · Accepted Answer · 2018-12-20 15:39:38Z

3

Checking for File/Dir Existence

The code you're employing to verify that a directory (?) exists is

set %~3= dir /p|find /C "%~2"

I don't think this is doing what you intend. SET /P is often used like this in order to pipe the output of a command into an environment variable. (Though, you are giving /P to dir, which paginates the output—probably not what you intended.) The command you have won't do that, though. I'd guess that what this is accomplishing is setting the var to (literally) " dir /p" and then piping that through find-count. That results of find.exe /C never make it back into the envvar though. The output line "0" is the result of piping (nothing) through find.exe /C.

I propose a simpler test for existence:

IF EXIST "%~2" (SET /A %~3=1) ELSE (SET /A %~3=0)

This test worked on my Win10 machine.

I have seen some variance in how IF EXIST works. If you didn't want to use that, you could do it with a FOR loop.

FOR /F "tokens=*" %%e IN ('DIR /B') DO IF "%%~e"=="%~2" SET /A %~3=1

If you want to use the pipe in the FOR command, you'll have to escape it.

FOR /F "tokens=*" %%e IN ('DIR /B ^| find /C "%~2"') DO SET /A %~3=%%~e

All three of these methods worked for me.

SETLOCAL

I do not think there exists an official reference guide for cmd syntax other than the built-in help (SETLOCAL /?)

My experience with it is that it pushes all the envvars and working directories onto a "stack" and a corresponding ENDLOCAL or EXIT (though in scripts, you almost always want to use EXIT /B) will pop the environment off that "stack." In effect, it means that envvar/CWD changes you make in a SETLOCAL will only be temporary.

answered Dec 20, 2018 at 15:39

mojo

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2 Comments

LasithaMD Over a year ago

though in scripts, you almost always want to use EXIT /B. This is because if exist /b is not defined at the end of the function, the usual execution flow will continue which is top to bottom and can eventually be end up in a recursion with max recursion depth reached.

LasithaMD Over a year ago

This trick IF EXIST "%~2" (SET /A %~3=1) ELSE (SET /A %~3=0) solved the problem.

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