Changes

<span style="font-family:courier;>'''ls a.txt b.txt c.txt 1.txt 2.txt 3.txt abc.txt work.txt'''<br>

a.txt b.txt c.txt 1.txt 2.txt 3.txt abc.txt work.txt</span>

But there is no need to type all of those file pathnames as separate arguments. You can use a special character to indicate to the Bash shell to match all files that end with the extension ".txt":