====== Szkriptelés ======

==== Gyors uniq awk-val ====

  awk '!x[$0]++'

==== Fájlba beszúrás minta után, ha még nincs ====
  sed -i '/^EZENSTRINGUTAN /{N; /\nBEILLESZTENDO$/b; s/\n/\nBEILLESZTENDO\n/}' /etc/resolv.conf

==== Futási logok archiválása havi lebontású .zip-be, és az 1 hónapnál régebbiek törlése ====

  zip -9rv ${LOG}/$(date +%Y%m)_archived_backup_logs.zip ${LOG}/${LOGFILE##*/}
  find ${LOG}/*.log -type f -mtime +60 -exec rm {} \;


==== Háttérben futunk-e? ====

  case $(ps -o stat= -p $$) in
  *+*) echo "Running in foreground" ;;
  *) echo "Running in background" ;;
  esac

==== crontab-ból futunk-e? ====

  CRON=$(pstree -s $$ | grep -q cron && echo true || echo false)

==== nohup-pal futunk-e? ====

  if egrep -q "SigIgn:\s.{15}[13579bdf]" /proc/$$/status ; then
    echo "Ignores SIGHUP (runing via nohup)" 
  else
    echo "Doesn't ignore SIGHUP (NOT running via nohup)"                                             
  fi

==== Fájl rendezése több soros csoportosításban ====

Pl: 4 oszlopos bemeneti fájl 3 soros csoportokban. A 3 sort egymás után rakjuk, lerendezzük az 5. oszlopra, majd újra eltördeljük
  paste - - - < input.file | sort -k5 | xargs -n4

==== Szkript kimeneteinek automatikus logolása fájlba ====

  A_CURR_SHELL=$(ps -o args= -p "$$" | sed 's/ .*$//' | sed 's#^.*\/##g')
  if [[ "$A_CURR_SHELL" == "bash" ]]; then
      exec > >(tee -ia $A_TMP_FILE)
      exec 2> >(tee -ia $A_TMP_FILE >&2)
  elif [[ "$A_CURR_SHELL" == "ksh" ]]; then
      mkfifo /tmp/$$-out-fifo
      ( exec tee -ia $A_TMP_FILE < /tmp/$$-out-fifo >&2 ) &
      exec 1>/tmp/$$-out-fifo
      exec 2>/tmp/$$-out-fifo
      rm -f /tmp/$$-out-fifo
  fi
  

forrás [[https://stackoverflow.com/questions/3173131/redirect-copy-of-stdout-to-log-file-from-within-bash-script-itself]]

==== Ismétlődő sorok számolása ====

  cat file | sed 's/([^(]*)$/,&/' | awk -F'[,]' '{a[$2]++}END{for(k in a) print $1,k,$3,"("a[k]"x)"}'

==== User input default értékkel ====

  DEFAULT="Semmit"
  read -e -p "Mit akarsz?" -i "$DEFAULT" VALTOZO
  VALTOZO="${VALTOZO:-$DEFAULT}"

==== Terminálról olvasás ciklusban ====

  read input </dev/tty

==== /dev/stdin üres-e? (Van-e adat a pipe-ban?) ====

  [ ! -t 0 ]

==== /dev/stdout -ja van-e a processznek? (Terminálban fut-e?) ====

==== Bekezdésre greppelés Linux alatt (AIX: grep -p) ====

  sed -n '/Storage Slots/{:a;N;/\n$/!ba;p}' 
  awk 'BEGIN{IGNORECASE=1;RS=ORS="\n\n";FS=OFS="\n"}/Storage Slots/'
  perl -00 -ne 'print if /Storage Slots/'

==== Bekezdésre exclude-olása Linux alatt ====

  awk -v RS= -v ORS='\n\n' 'NR==FNR{a[$0]++;next}!($0 in a)' file2 file1
==== Ha az SSH kilép aciklusból az első futás után ====

  ssh -n ...

==== Sztringek hexa értelmezésének kiküszöbölése ====

Pl:
  $((10#`date +%H`))

==== A grep "-o" kapcsolójának kiváltása perl-lel ====

  perl -lne '/reguláris kifejezés/ && print $&'

==== Processz környezeti változóinak listázása ====

  xargs -0 -L1 -a /proc/3242/environ
==== BASH változó manipulációk ====

^Syntax^Meaning^
|${#var} | String length (number of characters in $var).|
|${var%%,%%} | Lowercase first alphanumeric character in $var.|
|${var%%^%%} | Uppercase first alphanumeric character in $var.|
|${var%%^^%%} | Uppercase alphanumeric characters in $var.|
|${var%%^^%%[p,g]} | Uppercase alphanumeric characters in $var matching p or g.|
|${parameter?err_msg},${parameter:?err_msg} | If parameter set, use it, else print err_msg and abort the script with an exit status of 1. Both forms nearly equivalent. The : makes a difference only when parameter has been declared and is null.|
|${parameter-default},${parameter:-default} | If parameter not set, use default. ${parameter-default} and ${parameter:-default} are almost equivalent. The extra : makes a difference only when parameter has been declared, but is null.|
|${parameter=default},${parameter:=default} | If parameter not set, set it to default. Both forms nearly equivalent. The : makes a difference only when $parameter has been declared and is null.|
|${parameter+alt_value},${parameter:+alt_value} | If parameter set, use alt_value, else use null string. Both forms nearly equivalent. The : makes a difference only when parameter has been declared and is null.|
|${var#Pattern} | Remove from $var the shortest part of $Pattern that matches the front end of $var.|
|${var##Pattern} | Remove from $var the longest part of $Pattern that matches the front end of $var.|
|${var%Pattern} | Remove from $var the shortest part of $Pattern that matches the back end of $var.|
|${var%%%%Pattern} | Remove from $var the longest part of $Pattern that matches the back end of $var.|
|${var:pos} | Variable var expanded, starting from offset pos.|
|${var:pos:len} | Expansion to a max of len characters of variable var, from offset pos.|
|${var/Pattern/Replacement} | First match of Pattern, within var replaced with Replacement. If Replacement is omitted, then the first match of Pattern is replaced by nothing, that is, deleted.|
|${var%%//%%Pattern/Replacement} | Global replacement. All matches of Pattern, within var replaced with Replacement. If Replacement is omitted, then all occurrences of Pattern are replaced by nothing, that is, deleted.|
|${var/#Pattern/Replacement} | If prefix of var matches Pattern, then substitute Replacement for Pattern.|
|${var/%Pattern/Replacement} | If suffix of var matches Pattern, then substitute Replacement for Pattern.|
|${!varprefix*},${!varprefix@} | Matches names of all previously declared variables beginning with varprefix.|

forrás: [[http://tldp.org/LDP/abs/html/parameter-substitution.html]]

==== Gyakori BASH RC kódok ====

^Exit Code Number	^Meaning	^Example	^Comments^
|1	|Catchall for general errors	|let "var1 = 1/0"	|Miscellaneous errors, such as "divide by zero" and other impermissible operations|
|2	|Misuse of shell builtins (according to Bash documentation)	|empty_function() {}	|Missing keyword or command|
|126	|Command invoked cannot execute	|/dev/null	|Permission problem or command is not an executable|
|127	|"command not found"	|illegal_command	|Possible problem with $PATH or a typo|
|128	|Invalid argument to exit	|exit 3.14159	|exit takes only integer args in the range 0 - 255 (see first footnote)|
|128+n	|Fatal error signal "n"	|kill -9 $PPID of script	|$? returns 137 (128 + 9)|
|130	|Script terminated by Control-C	|Ctl-C	|Control-C is fatal error signal 2, (130 = 128 + 2, see above)|
|255*	|Exit status out of range	|exit -1	|exit takes only integer args in the range 0 - 255|

==== Színezés ====

ANSI2HTML [[https://github.com/pixelb/scripts/blob/master/scripts/ansi2html.sh]]
Színkódok [[https://misc.flogisoft.com/bash/tip_colors_and_formatting]]   

Hiba csatorna színezése:

   $ parancs 2> >(while read line; do echo -e "\e[01;31m$line\e[0m"; done)

Bash színkódok törlése szövegből:

  sed -r "s/\x1B(\[[0-9;]*[JKmsu]|\(B)//g"

Színkódok és sorvég karakterek kivágása szövegből:
A ^M-et így: CTRL+V, CTRL+M !!

  sed -i -e 's/\x1b\[[0-9;]*m//g' -e 's/^M//g' file

Váltott soroz színezés:

  | awk '{if (NR%2 != 1) {print "\033[48;5;235m" $0 "\033[0m"; next;} {print "\033[38;5;239m" $0 "\033[0m";}}'
==== Dátumos prompt képernyőmentéses dokumentáláshoz ====

  export PS1='[\u@\h \W] \D{%F %T}\n\$ '

==== Terminál doboz rajzolás ====
  
  env printf '\u2502'
  
Karakterek: https://en.wikipedia.org/wiki/Box-drawing_character
  
==== Terminál kurzor pozícionálás ====
  
- Position the Cursor:
  \033[<L>;<C>H
     Or
  \033[<L>;<C>f
  puts the cursor at line L and column C.
- Move the cursor up N lines:
  \033[<N>A
- Move the cursor down N lines:
  \033[<N>B
- Move the cursor forward N columns:
  \033[<N>C
- Move the cursor backward N columns:
  \033[<N>D

- Clear the screen, move to (0,0):
  \033[2J
- Erase to end of line:
  \033[K

- Save cursor position:
  \033[s
- Restore cursor position:
  \033[u

==== "Homokóra" - progress ikon ====
v1:
<file>
a=1
sp="/-\|"
echo -n ' '
while true
do
    printf "\b${sp:a++%${#sp}:1}"
done
</file>
v2:
<file>
spinner()
{
    local pid=$1
    local delay=0.75
    local spinstr='|/-\'
    while [ "$(ps a | awk '{print $1}' | grep $pid)" ]; do
        local temp=${spinstr#?}
        printf " [%c]  " "$spinstr"
        local spinstr=$temp${spinstr%"$temp"}
        sleep $delay
        printf "\b\b\b\b\b\b"
    done
    printf "    \b\b\b\b"
}
</file>

==== Parancsok csoportosítása ====

Új shellben:
  (parancs1)
  
Aktuális shellben:
  { parancs1; }

[[https://devhints.io/bash|Bash scripting cheatsheet]]