18.04: Why this command doesn't work?

Question

Sorry for this stupid question, but I spent a time to figure out!!

#! /bin/bash a=/etc cd $a

Normally, if I assign value for $a variable and then cd $a, it works. But when I create a separate file - it doesn't!

Why does it happen like this?

Answer 1

You're executing your script using #!/bin/bash which launches the new bash session invisible for you and changes its directory to $a and then exits. You just don't see it.

To achieve what you want, I've slightly modified your script:

$ cat test.sh
#!/bin/bash
a="/etc/"
cd $a
echo $a

$ chmod +x test.sh

And executed it using a . dot before script (or source keyword). It executes script inside of the current bash session:

Result:

user@ubuntu:~/test$ . test.sh 
/etc/
user@ubuntu:/etc$