SHIFT: Shifts the position of replaceable parameters in batch files.

Microsoft Windows [Version 10.0.19045.3693]
(c) Copyright 1985-2023 Microsoft Corp.

C:\\WINDOWS>

Changes the position of replaceable parameters in a batch file.

SHIFT [/n]

If Command Extensions are enabled the SHIFT command supports
the /n switch which tells the command to start shifting at the
nth argument, where n may be between zero and eight.  For example:

    SHIFT /2

would shift %3 to %2, %4 to %3, etc. and leave %0 and %1 unaffected.

The `SHIFT` command in Windows Command Prompt is used to move the position of parameters in a batch file. Here are some examples of using the `SHIFT` command: Example 1: Iterate through parameters in a batch file:

@ECHO OFF
:LOOP
IF "%1"=="" GOTO END
ECHO parameters: %1
SHIFT
GOTO LOOP
:END

Description: This example uses a loop to iterate through all parameters in a batch file and display them one by one. The `SHIFT` command is used to shift the position of the parameters. Example 2: Sum parameters in a batch file:

@ECHO OFF
SET SUM=0
:ADD_LOOP
IF "%1"=="" GOTO END_ADD
SET /A SUM+= %1
SHIFT
GOTO ADD_LOOP
:END_ADD
ECHO sum: %SUM%

Description: In this example the parameters are summed in a loop. The `SHIFT` command moves the parameter position, and `SET /A` is used to update the sum. Example 3: Working with nested loops and SHIFT:

@ECHO OFF
:OUTER_LOOP
IF "%1"=="" GOTO END_OUTER
ECHO Outer Parameters: %1
SHIFT
:INNER_LOOP
IF "%1"=="" GOTO END_INNER
ECHO Inner Parameter: %1
SHIFT
GOTO INNER_LOOP
:END_INNER
GOTO OUTER_LOOP
:END_OUTER

Description: This example shows how `SHIFT` can be used in nested loops. The outer loop processes outer parameters while the inner loop processes the inner parameters. Example 4: Skipping parameters with SHIFT:

@ECHO OFF
SHIFT
SHIFT
ECHO Third parameter: %1

Description: Here the first two parameters are skipped with two consecutive `SHIFT` commands and the third parameter is displayed. Example 5: Check and handle parameters:

@ECHO OFF
:PARAM_LOOP
IF "%1"=="" GOTO END_PARAM
IF /I "%1"=="/DEBUG" (
    ECHO debug mode activated.
    SHIFT
    GOTO PARAM_LOOP
)
ECHO Process parameters: %1
SHIFT
GOTO PARAM_LOOP
:END_PARAM

Description: This example checks whether the first parameter is "/DEBUG". If this is the case, a message is issued and the parameter is skipped. The `SHIFT` command is particularly useful in batch scripts where a variable number of parameters need to be processed. Note that `SHIFT` moves the contents of the parameter list and reassigns parameter positions. Therefore, it is important to use `SHIFT` wisely and according to the logic of your batch script.

There are a few important aspects to consider when using the `SHIFT` command in batch scripts: 1. Parameter loss: When you call `SHIFT`, this shifts the position of the parameters to the left in the parameter list. This means that the value of the first parameter (`%1`) is replaced by that of the second parameter (`%2`), the second parameter becomes the third (`%3`), and so on. The value of the last parameter (`%9`) is lost and the value of `%0` (the script name) remains unchanged. 2. Number of shifts: You can only call `SHIFT` nine times in a batch script because there are only nine numeric parameters (`%0` to `%9`). After the ninth shift, the value of the ninth parameter remains lost. 3. SHIFT in loops: When using `SHIFT` in a loop, you should ensure that the conditions are checked properly to avoid an infinite loop if there are no other parameters.

   @ECHO OFF
   :LOOP
   IF "%1"=="" GOTO END_LOOP
   ECHO parameters: %1
   SHIFT
   GOTO LOOP
   :END_LOOP
   

4. SHIFT in nested loops: When using `SHIFT` in nested loops, note that moving the parameters in a loop also affects the parameter positions in the nested loops.

   @ECHO OFF
   :OUTER_LOOP
   IF "%1"=="" GOTO END_OUTER
   ECHO Outer Parameters: %1
   SHIFT
   :INNER_LOOP
   IF "%1"=="" GOTO END_INNER
   ECHO Inner Parameter: %1
   SHIFT
   GOTO INNER_LOOP
   :END_INNER
   GOTO OUTER_LOOP
   :END_OUTER
   

5. Delayed expansion and SHIFT: If you use `SHIFT` in combination with delayed expansion (`ENABLEDELAYEDEXPANSION`), note that `!` is used for delayed expansion, not `%`.

   @ECHO OFF
   SETLOCAL ENABLEDELAYEDEXPANSION
   SET COUNT=0
   :LOOP
   IF "!1"=="" GOTO END_LOOP
   SET /A COUNT+=1
   SHIFT
   GOTO LOOP
   :END_LOOP
   ECHO Number of parameters: %COUNT%
   

It is important to carefully plan the order and frequency of `SHIFT` to ensure that the parameters are shifted as expected and no information is lost. Checking for empty parameters (`IF "%1"==""`) is also important to avoid infinite loops.