Appending a new line character to a variable in a for loop Windows batch

Question

I am looping through the results of a command and appending them all to one variable (!results!) within that loop. At the end of the loop, if the results are not empty then I print them. I would like each result to appear on a new line.

setlocal EnableDelayedExpansion
set results=
set lf=^

for /f "delims=" %%a in ('call mvn dependency:analyze ^| findstr "WARNING"')
    do ( set results=!results!!lf!%%a )
    if not [!results!]==[] (
        echo. ------------------------------------
        echo. FOUND MATCHES 
        echo. ------------------------------------
        echo. !results! 
        echo. ------------------------------------
        echo. ------------------------------------
        echo. && echo.
    )

I'm trying to use a new line batch hack that I've seen on here, but it doesn't seem to be working in this context.

What I'm getting

------------------------------------
FOUND MATCHES 
------------------------------------
[WARNING] Used undeclared dependencies found: [WARNING]    org.springframework:spring-jms:jar:3.0.5.RELEASE:compile   [WARNING]    org
    .springframework:spring-beans:jar:3.0.5.RELEASE:compile         [WARNING]    xml-apis:xml-apis:jar:1.3.04:compile
------------------------------------
------------------------------------

What I'd like

------------------------------------
FOUND MATCHES 
------------------------------------
[WARNING] Used undeclared dependencies found:
[WARNING]    org.springframework:spring-jms:jar:3.0.5.RELEASE:compile   
[WARNING]    org.springframework:spring-beans:jar:3.0.5.RELEASE:compile         
[WARNING]    xml-apis:xml-apis:jar:1.3.04:compile
------------------------------------
------------------------------------

Answer 1

To get it running at all, I had to add some setlocal statements and add extra blank line between set lf=^ and the for. Once I did that, I actually see different output than you:

 !results!!lf!%a
[WARNING] a
[WARNING] c

This can easily be fix to work on my (Win7) machine by simply adding the following before the for:

set results=

There will be a leading blank line in the output, but it surely be surprised by adding a conditional when data is added to results.

But given the difference in the output you get, I guess we'll need to take a different approach to get it working for you. This should be much more robust than playing with newlines anyway.

@echo off
setlocal
setlocal EnableDelayedExpansion

set showed_header=0
for /f "delims=" %%a in ('call mvn dependency:analyze ^| findstr "WARNING"') do (
   if !showed_header!==0 (
      set showed_header=1
      echo ------------------------------------
      echo FOUND MATCHES 
      echo ------------------------------------
   )

   echo %%a
)

if %showed_header%==1 (
   echo ------------------------------------
   echo ------------------------------------
   echo.
   echo.
)

Tested using perl -e"print qq{[WARNING] a\nb\n[WARNING] c\n}".