SHELL

bash or

if [ "$1" = "a.txt" ] || [ "$2" = "c.txt" ]; then
	# do smt...
fi

and in bash

Logical AND (&&)

if [1 -gt 0 ] && [ 2 -gt 1 ]; then 
	echo 1;
fi
 
 Logical OR (||)
 
 if [1 -gt 0 ] || [ 2 -gt 1 ]; then 
	echo 1;
 fi

and OR bash

[[ ! EXPR ]]	Not
[[ X && Y ]]	And
[[ X || Y ]]	Or