Can I pass a newline in a command line parameter to a Windows executable in a batch file?

Question

Say, I have an executable file that I want to pass a parameter to from a .bat file. The catch is that the parameter value must have a newline in it.

When I try the following:

"c:\folder\my app.exe" parameter="line1\nline2"

the result doesn't get interpreted as having a new line between line1 and line2.

Any ideas how to do it?

Answer 1

No, not via batch file itself. But exe files or other programs can pass arguments containing new lines to other Exe files.

So your solution here is to create trivial tool parsing your arguments which you will call like

runner "c:\folder\my app.exe" parameter="line1\nline2"

and it will substitute \n for true LF character (here shown as ↵) and execute the call using P/Invoke:

"c:\folder\my app.exe" parameter="line1↵line2"

Another way to overcome this limitation is using PowerShell. It has different command line parsing.

Answer 2

Yes, you can.
Use a small batch file to define a \n variable.

@echo off

(set \n=^^^
%=empty, do not delete this line =%
^
%=empty, do not delete this line =%
)

myApp.exe Line1%\n%Line2

It even works, if the parameter contains quotes.
The quotes has to be escaped.

myApp.exe parameter=^"aaa%\n%bbb^"

The definition of the new line looks a bit complex, but it caused by the rules of the caret

Answer 3

Can't be done.

Similar to why the chown Unix command uses a colon as a separator: chown assumes usernames end with colons. Likewise, batch files have a file format.

The file format of a batch file assumes that the newline character ends a line. There is no supported escape sequence. So, what you're asking for cannot be done.

One possible workaround is if the program recognizes an escape sequence, such as recognizing \n. (JScript, supported as .js files that CScript can use, supports the unescape command. WScript.Echo(unescape("%0d0a"));)

Another common approach to handle this is if a program supports a data stream, which could be a specified filename or the "standard input" stream. Newline characters/sequences can be provided to a program that way.

Those approaches are used by multiple programs. I'm not offhand recalling any way to just have batch ignore a newline character, nor any other standardized way to try to encode that character in a way that all/most programs will recognize the character(s) that you're trying to refer to.