http://rogerdudler.github.io/git-guide/

if [ $UID -eq 0 ];then echo "root";fi

  ping -c 1 ${HOST} -W 1 >/dev/null
  if [ $? == 0 ];
  then
 
  fi

clr_red=$'\e[1;31m'
clr_green=$'\e[1;32m'
clr_yellow=$'\e[1;33m'
clr_blue=$'\e[1;34m'
clr_reset=$'\e[0m'

 echo ${clr_red}test${clr_reset}

#!/bin/bash
[[ -n "$DEBUG" ]] && set -x
echo "test ($DEBUG)"
[[ -n "$DEBUG" ]] && set +x

calling this script with DEBUG-variable set switches to xtrace mode (print commands before they are executed)

DEBUG=1 ./test.sh

log single command (only stderr) and view simultaneously (stdout+stderr)

#via Process Substitution (https://www.gnu.org/software/bash/manual/bash.html#Process-Substitution)
make 2> >( tee "$logfile" ) ; echo $?

log multiple lines/commands:

exec 3> >(tee logfile)
 
make alpha 2>&3 &&
make bravo 2>&3 &&
make charlie 2>&3 && success=1
 
exec 3>&-

case "$string" in 
  *foo*)
    #anything
  ;;
  [1-6]*)
    #number-ranges
  ;;
  *)
    #all other
  ;;
esac

In Bash 4: all lowercase

$ echo "${string,,}"

all uppercase:

$ echo "${string^^}"

Quelle

  $ VAR=/home/me/mydir/file.c
  $ DIR=$(dirname "${VAR}")
  $ echo "${DIR}"
  /home/me/mydir
  $ basename "${VAR}"
  file.c

a=string
b=${a:p:l}
#p=Position (0-basiert),l=Länge

orig="AxxBCyyyDEFzzLMN"
mod=${orig//[xyz]/_}

string='My string';
 
if [[ $string =~ .*My.* ]]
then
  echo "It's there!"
fi

GPIO_NO=$((232+25))

ls IMG_20170923_{17..18}*

temporary change language (e.g. to get errors in english for forums):

LANG=C