Question

As mentioned in several forums and here, on stackoverflow, there’s no difference between these two ways of command substituion in shell.

But, there is. Here is a real example:

# this command works fine:
$(cat $LOG_FILE | gawk "(\$1 \$2) > $TIME")

# this one does not:
`cat $LOG_FILE | gawk "(\$1 \$2) > $TIME"`

Answer 1

And the whole thing behind this is that when bash sees a first `, it tries to find another one, substituting all \$, \` and \\ on its way,

which leads to replacing \$1 with $1, and then,

when substituting everything inside a "...", $1 is no longer escaped and is treated as the first agrument in a shell script itself (which is an empty string in my case) instead of being passed as $1 to gawk as is.

This is another reason for not using `...` in shell.