===== Shell (Command Line Interpreter) =====

  * https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_05_02
  * Reference : http://www.gnu.org/software/bash/manual/html_node/Special-Parameters.html#Special-Parameters
  * http://www.blaess.fr/christophe/memo_programmation_shell.html
  * https://github.com/lmorg/murex# JsoN

==== KSH ====

  * korn : http://www.last.fm/user/nmental/journal/2007/09/30/a52jn_linux_humor_ed._2_%28korn_meets_korn%29


==== GNU TOOLS ====

==== variables ====

args :
  "$@"

From shell :
  a=SHELL ; b=$(eval "echo \${${a}}" ); echo $b
  /bin/bash

Same with makefiles :
  a=SHELL ; b=$$(eval "echo \$${$${a}}" ); echo $$b

But it will fail if using gmake env
  a=CURDIR ; b=$$(eval "echo \$${$${a}}" ); echo $$b


   export ${USER}_KEY=${EMAIL}
   t=${USER}_KEY
   VAL=$(eval echo \${t} )
   echo $VAL

   ps $(</var/run/exim4/exim.pid)



==== COREUTILS ====

  expr --version # expr (GNU coreutils) 8.13
  
  expr 0 + 1 && echo "ok as expected  [$?]" # 0
  expr 1 + 0 && echo "ok as expected  [$?]" # 0
  expr 0 + 0 || echo "ko unexpected [$?]" # 1
  
  expr 0 || echo "ko unexpected [$?]" # 1 

http://www.gnu.org/software/coreutils/manual/coreutils.html#expr-invocation

       Exit status is 0 if EXPRESSION is neither null nor 0, 1 if EXPRESSION is null or 0, 2 if EXPRESSION is syntactically invalid, and 3 if an error occurred.

  echo "i="{1,2,3}
  i=1 i=2 i=3


@tag: WtF



==== Escape ====

  mkdir -p $(dirname "${mypath}") 

will fail, use workaround :

  dir=$(dirname "${mypath}") && mkdir -p "$dir"


==== Flow Control : ====

if:

  if ! true ; then echo then ; else echo else ; fi # print : else


    t=1 ; if [ "$t" != "0" ] && [ "$t" != "" ] ;  then echo "zero" ; fi

for in :

  export ARG=DllCanUnloadNow ; for f in *.lib  ;  do  echo "# $f:" ; dumpbin /symbols $f | grep $ARG ;  done

for using seq (or w/ [[bash]] (1..255) ):

  p=192.168.0 ; for i in $(seq 1 255) ; do ping -c 1  $p.$i > /dev/null 2>&1 && echo "$p.$i" ; done


for () :
  for (( i=0; $i <= 999 ; i++ )) ; do echo $i ; done


while : ( will eat one line each line)

  cat $F | while l=`line` ; do  echo -E "$l" >> $F.tmp ; t=`line` ; done ; mv $F $F.orig ; mv $F.tmp $F


case :

    case "$m" in
        jan | Jan)
            m=01; ;;
            
UntiL :
            
  until ping -w 1 -c 1 "$server" &>/dev/null ;do
    sleep 1
    n=$(( n+1 ))
    [ $n -eq 30 ] && break
  done
            
            

<code>
#! /bin/bash
FILE=$1
# read $FILE using the file descriptors
exec 3<&0
exec 0<$FILE
while read line
do
	# use $line variable to process line
	echo $line
done
exec 0<&3
</code>


  * https://www.vidarholen.net/contents/blog/?p=1035

==== eval ====

<code>
    list='PWD USER'
    for key in ${list} ; do
        value=$(eval echo \$${key})
        echo "${key}=${value}"
    done
</code>



===== Line =====

  ls | awk '{ system ($0 ) }' 

  ls | while L=`line`; do     echo $L;         read t ;     exit;     done; # will not work 


Line per line : use  IFS=$'\n'

  * http://www.osxfaq.com/tips/unix-tricks/week98/thursday.ws

<code>
prefix="date" ; IFS=$'\n' ; while [ 1 ] ; do date ; sleep 1 ; done | while read line ; do p="$(date +%Y%m%d%H%M%S)" &&  echo "$p: $prefix: $line" ; done
20131210122521: date: Tue Dec 10 12:25:21 CET 2013
20131210122522: date: Tue Dec 10 12:25:22 CET 2013
</code>


===== Pipe =====

  ls /dontexist ; echo $? # = 2
  ls /dontexist | tee log ; echo $? # = 0
  ls /dontexist | tee log ; echo $PIPESTATUS # = 2


For Plain Sh or BusyBox

<code>

Workaound for '/bin/sh' or busybox

status=0
eval ` { ls /dontexists || echo status="$?"; } | tee /dev/null`
echo "# status=${status}"

Trace :

busybox sh ~/bin/test.sh 
+ status=0
+ ls /dontexists
+ tee /dev/null
ls: /dontexists: No such file or directory
+ echo status=1
+ eval status=1
+ status=1
+ echo # status=1
# status=1


</code>

  * https://superuser.com/questions/704460/how-do-you-use-pipestatus-tee-and-bin-sh-together/925140#925140
  * https://www.perkin.org.uk/posts/how-to-fix-stdio-buffering.html# BuffeR AwK

@TaG: PipE


===== Multitask =====

  #{
  test_()
  {
  while [ 1 ]
  do
  echo "$*=$$"
  sleep 1
  done
  }


  main_()
  {
  test_ 1 &
  test_ 2
  }


  $*
  #}

  /tmp/t.sh main_




===== Text manipulation =====

recurvive grep :

  find ~/bin/ -type f  -exec grep -Hn  rzr {} \;

search & replace :

  sed -e "s/rzr/RzR/g" < filein.txt >| fileout.txt
  sed -e "s/rzr/RzR/g" -i fileinout.txt


pipes and `` :

  #! /bin/sh
  #file://~/bin/killall.sh
  kill -9 `ps aux | grep $* | cut -b0-10`

  killall.sh gdb

variables on sh bash

  VARNAME=value
  echo ${VARNAME}
  export VARNAME #

variables on csh tcsh
  set VARNAME value
  echo $VARNAME
  setenv VARNAME value

[[regex]] on Variables :

  echo ${EMAIL}
  # root@localhost
  echo ${EMAIL/@/(a)}
  # root(a)localhost

=== Variables===

  $ echo $RM
  $ echo ${RM:=rm}
  rm
  $ echo $RM
  rm
  $ RM=delete.sh
  $ echo ${RM:=rm}
  delete.sh
  $ echo $RM
  delete.sh
==== stdout ====


  printf "%c\n" $'\x31' # 1

  decimal=49
  eval printf \"%c\\n\" \$\'\\x$(printf "%02x" $decimal )\' # 1

  eval printf \"%c\\n\" \$\'\\x$(echo "obase=16;$decimal" | bc)\' # 1


  tar cf - $(find . -iname "*.h")  | tar xvf - -C  ${DESTDIR}/include

==== SED / [[AWK]] ====

  find . -name "*,*" -type d -exec basename {} \; | awk '{ printf "mv " $1 " " ; sub (/_/,"-") ; print $1 }'

  echo "9.999" | awk '{ printf "%.3f \n", $1 / 3 }'

remove each file 

  cat TODO | awk '{ system(" echo  " "rm -v \\\""  $1 "\\\" " ) }'


  * http://stackoverflow.com/questions/1429556/shell-bash-command-to-get-nth-line-of-stdout


head -50 | tail -1 = sed '50q;d' 

@more: AwK SeD [[sh]]
==== USEFULL BLACK MAGIC COMMANDS ====

Will rename [[C]] to [[C++]] files name conventions

  # ls *.c | xargs -n 1 --replace echo "mv {} {}pp"
  mv mainc.c mainc.cpp

  for i in *.ent; do	mv $i ${i/ent/gml} ; done

  rename 's/\.ent$/.gml/' *

  man mmv

  grep -v "^$" # remove empty lines

prints executables :
  find . -perm +100  -type f -exec file {} \; | grep "ELF 32-bit LSB"  | cut -d':' -f 1 

Copy all nodes :

  s=/mnt/sdb6/
  d=/mnt/sdb2/
  cd "$s" && time tar cf - . | { cd "$d" && tar xfv - ; }
  
  cat files.txt | awk '{  print "tar cvf - " $0 " | tar xvf - -C /tmp "}' > /tmp/movefiles.sh


==== COOL OPTIONS ====

  ifconfig | grep -A1 "^eth" #                                                                                                                            
  eth0      Link encap:Ethernet  HWaddr b8:70:??:??:??:??                                                                                                                                         
            UP BROADCAST MULTICAST  MTU:1500  Metric:1        

==== SCRIPT SHELL ====

A script shell is a simple series of shell commands :
see :

# cat file.sh
  #! /bin/sh
  echo "I am a script shell"
  date

# sh ./file.sh
  I am a script shell
  32 Dec 2000



search / replace with sed in multiple files :

  for fl in *.*; do
  mv $fl $fl.orig
  sed 's/FINDSTRING/REPLACESTRING/g' $fl.orig > "$fl"
  #rm -f $fl.orig
  done

  sed -i 's/gif/png/g' *.wrl


How to substract : 09 - 1 to return 08

  totem  mms://vipmms.canalplus.fr/canalplus/zapping_`expr  $(date +%y%m%d) - 1`_a.wmv



==== PER HOST ENV ====


  cat ../chhome/env-chhome.sh
  #===/bin/sh===
  # echo "+ file://~/env-chhome.sh"

  t=${HOME}/etc/home/$HOSTNAME/$USER
  # t=/home/$USER/etc/home/$HOSTNAME/$USER
  [[ -d $t ]] && HOME=$t && export HOME

  # file://~/.profile     : ok:console+login+bash
  # file://~/.login       : ko:console+login+bash
  # file://~/.xsession    : on [[Debian]]
  # file://~/.xinitrc     :

  # t=env-chhome.sh
  # [[ -f $t ]] && source $t

  # echo "- file://~/env-chhome.sh"

=== Joke ===

  echo '[q]sa[ln0=aln256%Pln256/snlbx]sb3135071790101768542287578439snlbxq'|dc 
===== MISC =====

  * http://rzr.online.fr/isbn/2841772772 # [[Livre]] :  http://www.amazon.fr/exec/obidos/ASIN/2841772772/rzr-21/#
  * http://directory.fsf.org/text/editors/lesspipe.sh.html
  * http://arstechnica.com/guides/other/msh.ars/2
  * http://linuxgazette.net/133/cherian.html # Bash
  * http://www.linuxjournal.com/article/6158
  * http://chris-lamb.co.uk/2008/01/24/can-you-get-cp-to-give-a-progress-bar-like-wget/
  * http://zsh.sourceforge.net/FAQ/zshfaq03.html# 3.24: What's wrong with cut and paste on my xterm?
  * http://www.ibm.com/developerworks/aix/library/au-badunixhabits.html # AwK vs GreP
  * https://github.com/pbrisbin/scripts# ScripT
  * http://www.unixmen.com/10-great-and-powerful-linux-commands-you-may-need-to-know/
  * http://felixcrux.com/blog/syntax-highlighting-cat# [[ZSh]]
  * http://datavu.blogspot.fr/2014/08/useful-unix-commands-for-exploring-data.html


===== TEXT =====

Here is the way to reverse "od" output :


    echo "test" | od -A x -t x1 | sed -e 's|^[0-f]* ?||g' | xxd -r
    test


  * http://stackoverflow.com/questions/794902/whats-the-opposite-of-od1/25100021#25100021

===== DATA FLOW =====

   while read -n 1 byte ; do printf "%b" "$byte" ; done < "$input" > "$output" # BiN :

  * http://unix.stackexchange.com/questions/10801/how-to-use-bash-script-to-read-binary-file-content
  * https://stackoverflow.com/questions/314675/how-to-redirect-output-of-an-entire-shell-script-within-the-script-itself#



===== LINKS =====

  * https://github.com/BYVoid/Batsh# BaT BasH CompileR
  * http://ohmyz.sh/# ZsH
  * http://code.joejag.com/2014/why-zsh.html# ZsH
  * http://linuxfr.org/news/liquid-prompt-1-9# PrompT
  * http://www.shellcheck.net/about.html# AnalysiS
  * https://github.com/shellinabox/shellinabox# WeB
  * https://news.ycombinator.com/item?id=18898523# AliaS
  * https://github.com/zerobyte-id/SEcraper# SearcH
  * https://docs.microsoft.com/en-us/powershell/scripting/install/installing-powershell-core-on-linux?view=powershell-7.1# PowerShell
  * https://mhoffman.github.io/2015/05/21/how-to-navigate-directories-with-the-shell.html# ToDo
  * https://github.com/Nukesor/pueue# QueuE ToDo TesT
  * https://tratt.net/laurie/blog/2024/faster_shell_startup_with_shell_switching.html#
  * https://learnbyexample.github.io/awk-idioms-explained/# AwK
  * https://learnbyexample.github.io/learn_gnused/breere-regular-expressions.html# SeD


===== MorE =====

@TaG : [[RegEx]] [[Perl]] [[DOS]] [[Unix]] [[AWK]] [[sed]] [[awk]] [[bash]] [[javascript]] [[script]] PrograM ScripT

{{http://www.helmsmusic.com/images/aug13_hell_station.jpg}}