CODEWITHSUNDEEP
windowsbatch-file
MxLDevs
MxLDevs

Reputation: 19506

Windows Batch Files: if else

I'm doing a simple batch file that requires one argument (you can provide more, but I ignore them).

For testing, this is what I have so far.

if not %1 == "" (
    dir /s/b %1
) else (
    echo no
)

Basically, I want to say if an argument is provided, recursively display all the files in the folder. Otherwise, say no.

It works when I provide an argument, but if I don't provide one it'll just tell me ( was unexpected at this time.

I mean, it works, but I wanted to at least display a user-friendly message explaining why it doesn't work. How should I change the code?

Upvotes: 63

Views: 201699

Answers (6)

mivk
mivk

Reputation: 14824

An alternative would be to set a variable, and check whether it is defined:

SET ARG=%1
IF DEFINED ARG (echo "It is defined: %1") ELSE (echo "%%1 is not defined")

Unfortunately, using %1 directly with DEFINED doesn't work.

Upvotes: 4

skchoe
skchoe

Reputation: 11

you have to do like this...

if not "A%1" == "A"

if the input argument %1 is null, your code will have problem.

Upvotes: 1

David angulo
David angulo

Reputation: 169

You have to do the following:

if "%1" == "" (
    echo The variable is empty
) ELSE (
    echo The variable contains %1
)

Upvotes: 16

Darin
Darin

Reputation: 91

Another related tip is to use "%~1" instead of "%1". Type "CALL /?" at the command line in Windows to get more details.

Upvotes: 9

jwd
jwd

Reputation: 11114

Surround your %1 with something.

Eg:

if not "%1" == ""

Another one I've seen fairly often:

if not {%1} == {}

And so on...

The problem, as you can likely guess, is that the %1 is literally replaced with emptiness. It is not 'an empty string' it is actually a blank spot in your source file at that point.

Then after the replacement, the interpreter tries to parse the if statement and gets confused.

Upvotes: 21

schnaader
schnaader

Reputation: 49719

if not %1 == "" (

must be

if not "%1" == "" (

If an argument isn't given, it's completely empty, not even "" (which represents an empty string in most programming languages). So we use the surrounding quotes to detect an empty argument.

Upvotes: 77

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