CODEWITHSUNDEEP
variablesbatch-file
thebattel2
thebattel2

Reputation: 3

Variable set in batch file won't show

When I do this in Notepad, the command prompt doesn't show ping %ip% -t -l %package%, but it shows ping %ip% -t -l and doesn't show the package variable.

@echo off
set data=0
set package = -600

IF %data% == 0 (
    set /a package= %package% + 1600
    @echo ping %ip% -t -l %package%
    )

echo %package%
pause

What am I doing wrong?

Upvotes: 0

Views: 124

Answers (1)

Magoo
Magoo

Reputation: 79983

Batch is sensitive to spaces in a SET statement. SET FLAG = N sets a variable named "FLAGSpace" to a value of "SpaceN"

The set "var=value" syntax ensures that any trailing spaces on the batch line are not included in the value assigned to var.

Within a block statement (a parenthesised series of statements), the entire block is parsed and then executed. Any %var% within the block will be replaced by that variable's value at the time the block is parsed - before the block is executed - the same thing applies to a FOR ... DO (block).

Hence, IF (something) else (somethingelse) will be executed using the values of %variables% at the time the IF is encountered.

Two common ways to overcome this are 1) to use setlocal enabledelayedexpansion and use !var! in place of %var% to access the changed value of var or 2) to call a subroutine to perform further processing using the changed values.

Note therefore the use of CALL ECHO %%var%% which displays the changed value of var.

So:

@echo off
SETLOCAL ENABLEDELAYEDEXPANSION
set /A data=0
set /A package=-600

IF %data% == 0 (
    set /a package=!package!+1600
    echo ping %ip% -t -l !package!
    )

echo %package%
pause

Noting: The setlocal statement should normally be placed at the start of the code. Your posted code is evidently a snip, since you do not appear to be setting ip.

Spaces are irrelevant in a set /a but even so, removing them fosters a habit

Set /a uses the run-time value, not the parse-time value of var when the syntax set /a var=var+1 is used within a loop, so set /a var=var+1 and set /a var=!var!+1 are equivalent but set /a var=%var%+1 uses the value of var at the time the loop is parsed.

Since echoing is set to off by the initial statement, the leading @ on the second echo is redundant.

Upvotes: 1

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