Extract leading numbers from a string in batch script

Question

I am new to batch scripting. although i have shell and python solutions for this problem but got stuck in batch script.

I have string like 123_happy,

Answer 1

probably the easiest and the fastest way:

set z=123_happy
for /l %%# in (%z%,1,%z%) do echo %%#

this will leave only the leading numbers.Though it is limited to 32b integers. As a subroutine (will fail if the input contains delimiters):

:extractLeadingNumbers input [rtrnVar]
  for /l %%# in (%~1;1;%~1) do (
     if "%~2" neq "" (
       set "%%#=%~2"
     ) else (
       echo %%#
     )
  )

More robust way (which will also remove leading zeroes):

cmd /c exit /b 123_happy
echo %errorlevel%