Hidden features of Windows batch files

The FOR command! While I hate writing batch files, I'm thankful for it.

FOR /F "eol=; tokens=2,3* delims=, " %i in (myfile.txt) do @echo %i %j %k

would parse each line in myfile.txt, ignoring lines that begin with a semicolon, passing the 2nd and 3rd token from each line to the for body, with tokens delimited by commas and/or spaces. Notice the for body statements reference %i to get the 2nd token, %j to get the 3rd token, and %k to get all remaining tokens after the 3rd.

You can also use this to iterate over directories, directory contents, etc...

Rather than litter a script with REM or :: lines, I do the following at the top of each script:

@echo OFF
goto :START

Description of the script.

Usage:
   myscript -parm1|parm2 > result.txt

:START

Note how you can use the pipe and redirection characters without escaping them.

The path (with drive) where the script is : ~dp0

set BAT_HOME=%~dp0
echo %BAT_HOME%
cd %BAT_HOME%

PAUSE

Stops execution and displays the following prompt:

Press any key to continue . . .

Useful if you want to run a batch by double-clicking it in Windows Explorer and want to actually see the output rather than just a flash of the command window.

if block structure:

if "%VS90COMNTOOLS%"=="" (
  echo: Visual Studio 2008 is not installed
  exit /b
)

Delayed expansion of variables (with substrings thrown in for good measure):

    @echo off
    setlocal enableextensions enabledelayedexpansion
    set full=/u01/users/pax
:loop1
    if not "!full:~-1!" == "/" (
        set full2=!full:~-1!!full2!
        set full=!full:~,-1!
        goto :loop1
    )
    echo !full!
    endlocal

SHIFT

It's a way to iterate through a variable number of arguments passed into a script (or sub-routine) on the command line. In its simplest usage, it shifts %2 to be %1, %3 to be %2, and so-on. (You can also pass in a parameter to SHIFT to skip multiple arguments.) This makes the command "destructive" (i.e. %1 goes away forever), but it allows you to avoid hard-coding a maximum number of supported arguments.

Here's a short example to process command-line arguments one at a time:

:ParseArgs

if "%1"=="" (
    goto :DoneParsingArgs
)

rem ... do something with %1 ...

shift

goto :ParseArgs


:DoneParsingArgs

rem ...

Findstr with regular expression support:

findstr "^[0-9].*" c:\windows\system32\drivers\etc\hosts

Bail on error.

IF "%errorlevel%" NEQ "0" (
   echo "ERROR:  Something broke.  Bailing out."
   exit /B 1
)

Append files using copy:

copy file1.txt+file2.txt+file3.txt append.txt

Also, to set all CLI parameters to a single variable:

SET MSG=%*

This will take every word (or symbol) that is separated by spaces and save it to a single batch file variable. Technically, each parameter is %1, %2, $3, etc., but this SET command uses a wildcard to reference every parameter in stdin.

Batch File:

@SET MSG=%*
@echo %MSG%

Command Line:

C:\test>test.bat Hello World!
Hello World!

I use them as quick shortcuts to commonly used directories. An example file named "sandbox.bat" which lives in a directory in my PATH

EXPLORER "C:\Documents and Settings\myusername\Desktop\sandbox"

Invoking the script is just WIN+R --> sandbox