bin/chess-quote

#!/usr/bin/env bash
#              bash 4.3.11(1)   Linux 3.13.0 Ubuntu 14.04.3   Date : 2017-08-18
#
# _______________|  chess-quote : Chess quote(s) from https://git.io/chess
#
#           Usage:  chess-quote [regex='.'] [N=1] 
#                          where regex means regular expression.
#
#       Exammples:  $ ./chess-quote         # One random quote
#                   $ ./chess-quote mate 2  # Two random quotes on "mate"
#                   $ ./chess-quote . 3     # Three very random quotes
#
#    Dependencies:  curl
#                   shuf
#
#  CHANGE LOG  LATEST version available: https://github.com/rsvp/chess
#  2017-08-18  First version.


#           _____ PREAMBLE_v3: settings, variables, and error handling.
#
LC_ALL=POSIX
#      locale means "ASCII, US English, no special rules, 
#      output per ISO and RFC standards." 
#      Esp. use ASCII encoding for glob and sorting characters. 
shopt -s   extglob
#     ^set extended glob for pattern matching.
shopt -s   failglob
#         ^failed pattern matching signals error.
set -e
#   ^errors checked: immediate exit if a command has non-zero status. 
set -o pipefail
#   ^exit status on fail within pipe, not (default) last command.
set -u
#   ^unassigned variables shall be errors.
#    Example of default VARIABLE ASSIGNMENT:  arg1=${1:-'foo'}

regex=${1:-'.'}
nquotes=${2:-'1'}

program=${0##*/}   #  similar to using basename
memf=$( mktemp /dev/shm/88_${program}_tmp.XXXXXXXXXX )
errf=$( mktemp /dev/shm/88_${program}_tmp.XXXXXXXXXX )


cleanup () {
     #  Delete temporary files, then optionally exit given status.
     local status=${1:-'0'}
     rm -f $memf $errf
     [ $status = '-1' ] ||  exit $status      #  thus -1 prevents exit.
} #--------------------------------------------------------------------
warn () {
     #  Message with basename to stderr.          Usage: warn "message"
     echo -e "\n !!  ${program}: $1 "  >&2
} #--------------------------------------------------------------------
die () {
     #  Exit with status of most recent command or custom status, after
     #  cleanup and warn.      Usage: command || die "message" [status]
     local status=${2:-"$?"}
     cat $errf >&2
     cleanup -1  &&   warn "$1"  &&  exit $status
} #--------------------------------------------------------------------
trap "die 'SIG disruption, but cleanup finished.' 114" 1 2 3 15
#    Cleanup after INTERRUPT: 1=SIGHUP, 2=SIGINT, 3=SIGQUIT, 15=SIGTERM
trap "die 'unhandled ERR via trap, but cleanup finished.' 116" ERR
#    Cleanup after command failure unless it's part of a test clause.
#
# _______________     ::  BEGIN  Script ::::::::::::::::::::::::::::::::::::::::


#  Retrieve the latest README.md and filter: 
curl -skL https://git.io/chessraw                 2>  $errf  \
     |  grep '^* '  |  grep -Ei "$regex" > $memf  2>> $errf  \
     ||  die "grep filtration FAIL: $regex" 113


#  Then select random number of quotes and format them:
shuf -n $nquotes $memf 2>> $errf  |  sed -e 's/^* //'


cleanup    #  Instead of: trap arg EXIT
# _______________ EOS ::  END of Script ::::::::::::::::::::::::::::::::::::::::

#  vim: set fileencoding=utf-8 ff=unix tw=78 ai syn=sh :