using "wc -l" on script counts more than using on terminal

Question

I'm making a bash script and it's like this:

#!/bin/bash
DNUM=$(ls -lAR / 2> /dev/null | grep '^d' | wc -l)
echo there are $DNUM directories.

the problem is, that when I run this line directly on the terminal:

ls -lAR / 2> /dev/null | grep '^d' | wc -l

I get a number.

But when I run the script it displays me a greater number, like 30 to 50 more.

What is the problem here?
Why is the "wc" command counting more lines when running it from a script?

Answer 1

You may have different directory roots for the two runs. Instead of ls to find the directories only you can use this

find parent_directory -type d

and pipe to wc -l to count.

The /proc directory will have processes and treated as directories and will change from run to run. To exclude it from the count use

find / -path /proc -prune -o -type d | wc -l