SHELL

replace filename space with underscore bash

for file in *; do mv "$file" `echo $file | tr ' ' '_'` ; done

linux replace spaces with underscore from all files in directory

find . -type f -name "* *" -exec bash -c 'mv "$0" "${0// /_}"' {} ;

replace space with underscore in linux

for file in *; do mv "$file" $(echo $file | tr ' ' '_') ; done

replace space with underscore command line in file name

@echo off
Setlocal enabledelayedexpansion

Set "Pattern= "
Set "Replace=_"

For %%a in (*.exe) Do (
    Set "File=%%~a"
    Ren "%%a" "!File:%Pattern%=%Replace%!"
)

Pause&Exit