How to properly nest Bash backticks

Question

Either I missed some backlash or backlashing does not seem to work with too much programmer-quote-looping.

$ echo \"hello1-`echo hello2-\\`echo hello3-\\`ech         


        

Answer 1

Any time you want to evaluate a command use command substitution:

$(command)

Any time you want to evaluate an arithmetic expression use expression substitution:

$((expr))

You can nest these like this:

Let's say file1.txt is 30 lines long and file2.txt is 10 lines long, than you can evaluate an expression like this:

$(( $(wc -l file1.txt) - $(wc -l file2.txt) ))

which would output 20 ( the difference in number of lines between two files).