rfcat

#!/usr/bin/env bash

:
##########################################################################
# Title      :  rfcat - print RFC text
# Version    :  2.6
# Author     :  Heiner Steven <heiner.steven@odn.de>
# Date       :  2001-04-25
# Requires   :  wget, gzip
# Category   :  WWW
# SCCS-Id.   :  @(#) rfcat  2.6 09/10/21
##########################################################################
# Description
#    o  Prints the text of an internet standard (RFC: "Request For
#   Comments") to standard output. Tries to locate the RFC locally,
#   and retrieves it otherwise direcly from the Web.
#    o  Each RFC text file can optionally be cached after first retrieval
##########################################################################

PN=`basename "$0"`          # Program name
VER='2.6'

# A program to accept an URL as command line argument, retrieves it, and
# prints the results to standard output
: ${GETURL:=wget}
: ${GETURLFLAGS="-O- -q"}   # may be empty

: ${COMPRESS:=gzip}
: ${COMPRESSFLAGS=-f}       # may be empty

# The local directory all RFCs are contained within
: ${RFCDIR:=/usr/local/share/rfc}

# The base WWW URL for all RFCs
RFC_BASE_URL=http://www.ietf.org

# The URL of the "INDEX" page
RFC_INDEX_URL=$RFC_BASE_URL/download/rfc-index.txt

# A template for an RFC URL. The string '${no}' will be replaced by the
# RFC's number
RFC_BY_NUMBER_TEMPL="$RFC_BASE_URL/rfc/rfc\${no}.txt"

#########################################################################

Usage () {
    echo >&2 "$PN - print RFC text, $VER (stv)
usage: $PN [-fc] rfcspec [...]
   -c:  create a local copy of the file, if it does not exist already
   -f:  force retrieval of the file from the Web

An rfcspec can be a RFC number (e.g. 2100), or the symbolic name
\"INDEX\". The RFC is searched locally (RFCDIR=$RFCDIR).
If this was not successful, $PN will retrieve it from $RFC_BASE_URL."
    exit 1
}

Msg () {
    for MsgLine
    do echo "$PN: $MsgLine" >&2
    done
}

Fatal () { Msg "$@"; exit 1; }

#########################################################################
# rfc2path - convert RFC specification to local path name of file
#########################################################################

rfc2path () {
    [ $# -eq 1 ] || Fatal "INTERNAL ERROR: rfc2path needs one argument"

    _rfcspec=$1; shift

    case "$_rfcspec" in
        INDEX)
        _url=$RFC_INDEX_URL;;
    *)
        no=$_rfcspec
        eval _url="$RFC_BY_NUMBER_TEMPL";
    esac
    echo $RFCDIR/rfc$_rfcspec
}

#########################################################################
# rfc2url - convert RFC specification to URL of file
#########################################################################

rfc2url () {
    [ $# -eq 1 ] || Fatal "INTERNAL ERROR: rfc2url needs one argument"

    _rfcspec=$1; shift

    case "$_rfcspec" in
        INDEX)
        _url=$RFC_INDEX_URL;;
    *)
        no=$_rfcspec
        eval _url="$RFC_BY_NUMBER_TEMPL";
    esac
    echo "$_url"
}

#########################################################################

set -- `getopt cfh "$@"` || Usage
[ $# -lt 1 ] && Usage           # "getopt" detected an error

CacheFile=false
ForceRetrieval=false
while [ $# -gt 0 ]
do
    case "$1" in
        -c) CacheFile=true;;
        -f) ForceRetrieval=true;;
    --) shift; break;;
    -h) Usage;;
    -*) Usage;;
    *)  break;;         # First file name
    esac
    shift
done

[ $# -lt 1 ] && Usage

errors=0
for rfc
do
    rfc=`echo "$rfc" | sed 's/^00*//g'` # remove leading zeroes

    #
    # Search RFC locally
    #

    file=`rfc2path "$rfc"`
    if [ -n "$file" ] && [ $ForceRetrieval = false ]
    then
    for ext in "" .gz .Z .z .txt.gz .txt.Z .txt.z
    do
        [ -r "$file$ext" ] || continue
        case "$ext" in
        "")     cat "$file$ext" ;;
        *.gz )  gunzip -c "$file$ext";;
        *.Z )   zcat "$file$ext";;
        *.z )   unpack "$file$ext";;
        esac
        [ $? -eq 0 ] || errors=`expr $errors + 1`
        continue 2          # Next RFC
    done
    fi

    #
    # No local file. Try to retrieve the RFC via URL
    #

    url=`rfc2url "$rfc"`
    if [ -n "$url" ]
    then
        # Get the RFC using the Web.
    # XXX: This page could be cached locally using
    #   ... | tee $RFCDIR/...

    if [ $CacheFile = true ]
    then
        # Retrieve file, and create a local copy.

        # Ignore keyboard signals, because they could cause the local copy
        # to be incomplete

        trap '' 1 2 3 13 15
        $GETURL $GETURLFLAGS "$url" | tee "$file"
        trap 1 2 3 13 15
        if [ -s "$file" ]
        then "$COMPRESS" $COMPRESSFLAGS "$file"
        else rm -f "$file"          # remove empty file
        fi
    else
        $GETURL $GETURLFLAGS "$url"
    fi
    [ $? -ne 0 ] && errors=`expr $errors + 1`

    fi
done
exit $errors