[GTALUG] Script to show HTTP(S) and TLS details for a website

[D. Hugh Redelmeier]

| From: William Park via talk <talk at gtalug.org>

| 1. You don't need quotes in variable assignments like 
| 	var="$(...)"
| 	var="$var1"

True.  Even if var1 has whitespace.  But the quotes are harmless.

The rule I aspire to following:
	Quote all shell variable references EXCEPT when they must not
	be quoted (rare).
It's a lot easier than knowing the very odd rules applying to
assignment and other special contexts.

Why is assignment odd?  Because, syntactically, it is a kind of word
(an ASSIGNMENT_WORD according to POSIX).

| 2. The following tests are the same.  They both tests if var is empty.
| 	[ "$var"x = x ]
| 	[ -z "$var" ]

I like -z

Superstitiously, I would write
	[ "x$var" = x ]
instead of
	[ "$var"x = x ]
I would otherwise worry that if $var started with, say, -, funny
things might happen.

| 3. Testing if command succeeded or failed can be done in-line.
| 	if command1 | command2 | command2; then
| 	    ...
| 	else
| 	    ...
| 	fi

When I learned sh (long before POSIX) I think that the Bourne Shell
set the exit status of a pipeline to the exit status of the first
command.  So I'm (needlessly) nervous about what the exit status of a
pipeline is.

BASH has an option to have a pipeline fail if any component fails.
Seems useful (but not portable): -o pipefail

Speaking of useful bash options, I always turn on these two options in
my BASH scripts
	-e stop dead when a command returns an error in an untested
		context
	-u consider a reference to an undefined variable to be an
		error
These catch a lot of errors that might otherwise go unnoticed.

| 4. Case statement is usually better than if statement.  eg.
| 	if [[ "$var" == glob ]]; then
| 	    ...
| 	fi
|    vs
| 	case $var in
| 	    glob) ... ;;
| 	esac
|     Note the missing quotes in case, too.  You don't need it.

I think that [[ ]] is a BASHism.  I presume that it has advantages
over [ ] but I don't know them.

In the old days, test (AKA [ ]) wasn't built-in and so case was
faster.  This isn't true of modern shells.