check-external-links.sh

#!/usr/bin/env zsh
#---------------------------------------------------------------------------
# Checks that all external links, those starting with http*, have "targets".
#---------------------------------------------------------------------------

default_path="docs"

help() {
	cat << EOF
A fairly crude, but mostly effective tool that checks URLs in markdown
files to make sure they all have "targets". It prints locations that
appears to be missing "{:target=...}".

It doesn't exit with an error if such links are found, because in some
cases, this might be intentional.

Usage: $script [-h|--help] [-n|--noop] [path1 ...]

Where the arguments are the following:
-h | --help            Print this message and exit
-n | --noop            Just print the commands but don't make changes.
-v | --verbose         Print the paths as they are processed. Mostly useful
                       when no problems are found and you are paranoid nothing
                       was checked. ;)
path1 ...              Check these paths. Directories will be visited recursively.
                       (Default: All markdown files under "$default_path")
EOF
}

error() {
	for arg in "$@"
	do
		echo "ERROR: $arg"
	done
	help
	exit 1
}

paths=()
: ${VERBOSE=}
while [[ $# -gt 0 ]]
do
	case $1 in
		-h|--h*)
			help
			exit 0
			;;
		-n|--n*)
			NOOP=echo
			;;
		-v|--v*)
			VERBOSE=echo
			;;
		-*)
			error "Unrecognized option: $1"
			;;
		*)
			paths+=("$1")
			;;
	esac
	shift
done

[[ ${#paths[@]} -gt 0 ]] || paths=("$default_path")

eg=$(which egrep)
# Use a somewhat complicated script to find the URLs starting
# with http, print only the matches and then filter out the 
# URLs that contain "target". It won't work perfectly, but ...
for path in "${paths[@]}"
do
	if [[ -n "$VERBOSE" ]]
	then
		dir=$([[ -d "$path" ]] && echo "(directory)")
		echo "$path $dir"
	fi
	$eg -nHoR '\(https?[^)]+\)(\S*)' \
		--include '*.markdown' --include '*.md' \
		--exclude-dir '_site' --exclude-dir '_sass' \
		$path | $eg -v target
done