===== LEARN =====

  * https://devhints.io/bash
  * https://github.com/dylanaraps/pure-bash-bible
  * https://news.ycombinator.com/item?id=25428621# MinimaL
  * https://betterprogramming.pub/24-bashism-to-avoid-for-posix-compliant-shell-scripts-8e7c09e0f49a#
  * https://bobcopeland.com/blog/2012/10/goto-in-bash/

==== OneLiner ====

  * https://github.com/onceupon/Bash-Oneliner
  * https://ocv.me/doc/unix/oneliners/

  for i in {0..65535} ; do printf "%x\n" $i ; done \
  | while read -r hex ; do printf "$hex(%d): \U$hex\n" 0x$hex ; done


==== arrays ===

<code>
list=(
 "item"
 "item with space"
)

for item in "${list[@]}" ; do
  echo "$item"
done
</code>

  echo 1 2 3 | { read -a words ; for value in "${words[@]}" ; do echo $value ; done } 
  
  end_date=($(date --date "$(date +%Y-%m-01) -1 day" "+%d %m %y"))
  start_date=(${end_date[*]})
  start_date[0]="01"
  
  echo ${start_date} # 01
  echo "${#start_date}" # 2

  echo ${start_date[*]} # 01 04 20
  echo "${#start_date[*]}" # 3
  
  echo ${end_date[*]} # 30 04 20
  echo "${start_date[@]:0:2}" # 01 04



  * http://wiki.bash-hackers.org/syntax/arrays
  * https://www.gnu.org/software/bash/manual/html_node/Arrays.html

@TaG: ArraY


==== bug ? ====

<code>
$SHELL --version && export LANG=C ; for i in $(seq 1 20) ; do  printf "[%d]\n" 0$i ; done 2>&1 | grep ": invalid"
GNU bash, version 3.2.48(1)-release (i486-pc-linux-gnu)
Copyright (C) 2007 Free Software Foundation, Inc.
bash: printf: 08: invalid number
bash: printf: 09: invalid number
bash: printf: 018: invalid number
bash: printf: 019: invalid number

$SHELL --version && export LANG=C ; for i in $(seq 1 20) ; do  printf "[%d]\n" 0$i ; done 2>&1 | grep ": invalid"
GNU bash, version 4.3.11(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
bash: printf: 08: invalid octal number
bash: printf: 09: invalid octal number
bash: printf: 018: invalid octal number
bash: printf: 019: invalid octal number


</code>

Fixed in :
  GNU bash, version 4.1.5(1)-release (i486-pc-linux-gnu)


GNU bash, version 4.2.37(1)-release (x86_64-pc-linux-gnu)

  bash: printf: 08: invalid octal number
  bash: printf: 09: invalid octal number

  printf "[%04d]\n" 9              
  [0009]

@TaG: PrintF

==== fork bomb ====

  :(){:|:&};: # fork bomb 

  url=http://view.atdmt.com/action/dlXP ; while [ true ] ;do wget -O /dev/null $url ; sleep 1 ; done



==== ${#foo} ====

<code>
display_string_by_packet()
{
    res_string=""
    packet_len=1
    [ "_" != "_${2}" ] && packet_len=$2
    if [ 0 -lt ${packet_len} ] ; then
        src_string=${1}
        pos=${#src_string}
        len=${packet_len}
        while [ 0 -lt ${pos} ] ; do
            pos=$((pos-${packet_len}))
            if [ 0 -ge ${pos} ] ; then
                len=$((${packet_len}+${pos}))
                pos=0
            fi
            res_string=${src_string:${pos}:${len}}" "${res_string}
        done
    fi
    echo -n ${res_string}
}


display_string_by_packet "this is a test" 2
#| th is i s a te st

</code>


==== variables ====

  echo ${foo:-bar}
  bar
  
=== $@ ===

  echo $@ | sort | while read t ; do cat "$t" ; done > "${file}"

https://www.gnu.org/software/bash/manual/html_node/Special-Parameters.html#index-_0040
==== getopts ====

  * https://www.gnu.org/software/bash/manual/html_node/Bourne-Shell-Builtins.html
  * https://wiki-dev.bash-hackers.org/howto/getopts_tutorial#


==== ops ====

  * https://www.gnu.org/savannah-checkouts/gnu/bash/manual/bash.html#Here-Documents <<<
===== env =====

<code>
# rzr@lap:tmp/ # [126] # mkdir  /tmp/bin/; touch /tmp/bin/script.sh
# rzr@lap:tmp/ # [0] #  PATH="/tmp/bin:$PATH" which script.sh
# rzr@lap:tmp/ # [1] #  PATH="/tmp/bin:$PATH" script.sh
bash: /tmp/bin/script.sh: Permission denied
</code>


===== MISC =====

  * http://wiki.bash-hackers.org/snipplets/start
  * https://github.com/vlisivka/bash-modules

Interactive Shell

        if [ "${-#*i}" != "$-" ]; then 

  * http://www.tldp.org/LDP/abs/html/intandnonint.html#IITEST
  * http://mywiki.wooledge.org/BashFAQ/002?action=diff&rev2=35&rev1=33
  * https://github.com/tdenniston/bish# TooL CompilE
  * https://n0where.net/bash-open-tcpudp-sockets# SockeT
  * https://github.com/aristocratos/bashtop# CurseS
  * https://github.com/petobens/trueline#
  * https://betterdev.blog/minimal-safe-bash-script-template/#


===== LINKS =====

  * https://github.com/oils-for-unix/oils/wiki/The-Biggest-Shell-Programs-in-the-World
  * https://github.com/lsferreira42/bash-ini-parser# ParseR




===== MORE =====

@TaG: [[Shell]] [[sh]] [[printf]] DeclarE

{{http://www.monsterbashnews.com/bash/Bash2006lobbyzach.jpg}}