Windows XP in a Nutshell

Name

shift

Synopsis

Delete the variable that holds the first command-line argument (%1) and shifts over the remaining arguments.

Syntax

shift

Description

Use the shift command when you want to cycle through all of the command-line arguments specified when the batch file was run. When a shift statement is encountered, the value stored in %2 is assigned to %1, the value stored in %3 is assigned to %2, and so on. The value stored in %1 before the shift statement is lost. This is particularly useful when processing loops.

Examples

In the following batch file, shift is used so that each of the command-line options becomes option #1 (%1) for processing within the loop. The beauty is that this works regardless of the number of arguments entered:

@echo off
rem MTYPE.BAT
rem example: mtype foo.txt bar.txt *.bat 
:loop
if "%1"=="" exit
for %%f in (%1) do type %%f 
shift
pause
goto loop

The if statement tests for an empty argument (meaning that shift has exhausted the supply of arguments) and ends the loop when found.

Notes

• Normally, the number of command-line arguments is limited to nine (%1 through %9), but shift makes it possible for a batch file to accommodate more.

• If you use a wildcard on the command line, it is passed to the batch file as a single argument (e.g., *.*), which can be used as is. It isn’t expanded first, as with Unix shells, so you can’t pick it apart in the script and use each matched filename separately.