Question

My keyboard only has normal quotes, not the smart ones.

I have observed that I need normal ones in CGI development and the backward ones in AWK/SED.

Is there a rule when I should use smart quotes, normal ones and backward ones?

Obviously, I need to edit my keyboard layout to get the smart quotes.

Answer 1

If you mean ` by smart quotes, then that is actually called ‘backquote’. Smart quotes are when you type ‘ and ‘, but get ‘ and ’ or “ and ” automatically depending on the context. I’m not sure how you would use smart quotes in awk or sed.

In the shell, backquotes, such as `command`, are used to evaluate a command and substitute the result of the command within them into the shell expression being evaluated; it can be used to compute and argument to another command, or to set a variable. For less ambiguity, you can instead use $(command), which makes a lot of quoting rules easier to work out.

In the shell, ' and ' are also different. ' is used for strings in which you want variable substitution and escape sequences. ' represents a string containing just the characters within the quotes, with not variable interpolation or escape sequences.

So, for example:

$ name=world $ echo 'Hello, $name' Hello, world $ echo 'Hello, $name' Hello, $name $ echo 'Testing \\ escapes' Testing \ escapes $ echo 'Testing \\ escapes' Testing \\ escapes $ echo `ls` example-file another-example $ echo 'ls' ls $ echo 'ls' ls 

Other scripting languages, such as Perl and Ruby, have similar rules, though there may be slight differences.