rfcreader.in

#!/bin/bash
##
## vim:foldmethod=marker:nowrap:
##
##--- Help
## usage: SCNAME [-f] rfcnum|rfcname [rfcnum|rfcname ...]
## 
## where	"rfcnum"	is the numerical part of the rfc you want to
## 				see,
## 		"rfcname"	is a name if a rfc file (for instance
## 				"rfc-index") and
## 		"-f"		forces the retrieval.
## 
## This script tries to retrieve the rfcs in question from configurable sources.
## First it tries to find them in the paths found in the environment variable
## "RFCPATHS" (by default "@RFCCACHEDIR@", multiple paths separated by
## colons), then it tries to retrieve them from selected URLs found in
## "RFCSOURCES" (by default "http://www.rfc-editor.org/rfc/", multiple sources
## separated by spaces).
## The RFCs retrieved from a RFCSOURCES are either permanently stored in the
## first writable directory in RFCPATHS or written to the "TMPDIR" (by default
## "/tmp") and deleted after the used viewer has terminated.
## On the local system the comma separated extensions in RFCEXTENSIONS are
## tried otherwise the first extension found in RFCEXTENSIONS is tried for
## remote retrieval.
##--- Help end
##
##--- Set some traps
trap 'test -n "${files2del}" && rm -f ${files2del}' INT QUIT ABRT KILL TERM EXIT
##--- Whats the name of this script?
SCNAME="${0##*/}"
##--- Some presets which might be overwritten
: ${RFCPATHS:='@RFCCACHEDIR@'}
: ${RFCEXTENSIONS:=".txt.gz .txt .html"}
: ${RFCSOURCES:='http://www.rfc-editor.org/rfc/ http://www.rfc-editor.org/rfc/std http://www.rfc-editor.org/rfc/bcp http://www.rfc-editor.org/rfc/fyi ftp://ftp.isi.edu/in-notes/'}
: ${RFCPAGER:="${PAGER:-less}"}
: ${TMPDIR:="/tmp"}
##--- Some special variables
RFCSFOUND=''
rfcpaths="$(echo "${RFCPATHS}" | tr : " ")"
files2del=''
prefix='rfc'
##--- Option switches
opt_force=''
opt_help=''
##--- Some functions
function help () {
	sed -r '
		/^##--- Help$/,/^##--- Help end$/ {
			s/^## //
			s/HELP_SCNAME/'"${SCNAME}"'/g
		}
		1,/^##--- Help$/ d
		/^##--- Help end$/,$ d' < $0
}
function findrfc () {
	# usage: findrfc rfcname
	# where "rfcname" is the name of one RFC you want to retrieve.
	# Returns a string which is the path and name of the locally found
	# rfc and return code zero or nothing a the return code ten. It
	# processes the global variable "rfcpaths" and "RFCEXTENSIONS".
	local rfcname="${1}" fullname='' retval='10'
	# Process all the paths in "RFCPATHS".
	for trypath in ${rfcpaths}; do
		# And try them with all the extensions in "RFCEXTENSIONS".
		for ext in ${RFCEXTENSIONS}; do
			# Construct the filename to test for.
			fullname="${trypath}/${rfcname}${ext}"
			# If the constructed name exists print this name, set
			# the return code to zero and end the two for loops.
			test -r ${fullname} && \
				{ echo "${fullname}"; retval='0'; break 2; }
		done
	done

	return ${retval}
}
function findwritable () {
	# usage: findwritable
	# No arguments are processed. Returns either the last path in RFCPATHS
	# which is writable for the current UID and return code zero or nothing
	# and return code ten.
	local retval='10' result=''
	# Process all the seperate paths in RFCPATHS.
	for pathname in ${rfcpaths}; do
		# If we find a path which is writable print this one, set
		# return code to zero and break the current for loop.
		test -w ${pathname} && { result="${pathname}"; retval='0'; }
	done

	echo "${result}"

	return ${retval}
}
function makename () {
	local retval='10' rfcname="${1}" varname="${2}" ext="${3}" writabledir=''
	local constructedname=''
	if writabledir="$(findwritable)"; then
		echo "${varname}='${writabledir}/${rfcname}${ext}'"
	else
		constructedname="${TMPDIR}/${rfcname}.${$}${ext}"
		echo "files2del='${files2del:+${files2del} }${constructedname}'; ${varname}='${constructedname}'"
	fi
}
function retrieverfc () {
	local retval='10' rfcname="${1}" varname="${2}"
	local localname=''; extension=''
	for resource in ${RFCSOURCES}; do
		for extension in ${RFCEXTENSIONS}; do
			eval $(makename ${rfcname} localname ${extension})
			if curl --location --silent --fail --output ${localname} "${resource}${rfcname}${extension}"; then
				echo "files2del='${files2del}'; ${varname}='${localname}'"
				retval='0'
				break 2
			fi
		done
	done

	return ${retval}
}
function showrfc () {
	local rfcfile="${1}"
	test "${RFCPAGER##*/}" = "less" && RFCPAGEROPTS="'${rfcfile##*/}', lines %lt-%lb of %L"
	$RFCPAGER${RFCPAGEROPTS:+ -PM"${RFCPAGEROPTS}"} ${rfcfile}
}
##--- Main program
process_opts="1"
while [ -n "${process_opts}" ]; do
	case "${1}" in
		-f|--force)
			opt_force='1';;
		--help|-h)
			opt_help='1';;
		--)
			process_opts='';;
		-*)
			echo "$SCNAME: Unknown option '${1}'"
			exit 10;;
		*)
			process_opts='';;
	esac
	test -n "$process_opts" && shift
done

if [ -n "$opt_help" ]; then
	help
	exit 0
fi

for rfcname in $*; do
	case "${rfcname}" in
		[0-9]*)
			rfcname="${prefix}${rfcname}";;
		*)
			:
			;;
	esac
	found="$(findrfc ${rfcname})"
	if [ $? -eq 0 -a -z "${opt_force}" ]; then
		RFCSFOUND="${RFCSFOUND:+${RFCSFOUND} }${found}"
	else
		if eval $(retrieverfc ${rfcname} found); then
			RFCSFOUND="${RFCSFOUND:+$RFCSFOUND }${found}"
		else
			echo "${SCNAME}: rfc '${rfcname}' not found" >&2
		fi
	fi
done

for rfcfile in ${RFCSFOUND}; do
	if [ -n "${firstshown}" ]; then
		if REPLY="$(read -ersp "--${SCNAME}-- next: ${rfcfile##*/} [ view (return) | skip (Ctrl-D) | quit (Ctrl-C) ]" || REPLY='skiped'; echo "${REPLY}")"; then
			if [ "${REPLY}" == "skiped" ]; then
				echo
				continue
			elif [ -z "${REPLY}" ]; then
				showrfc "${rfcfile}"
			fi
		else
			echo
			break
		fi
	else
		showrfc "${rfcfile}"
	fi
	firstshown='1'
done