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Bash

Reference

• Advance Bash scripting

  https://tldp.org/LDP/abs/html/index.html

• ShellCheck

  https://www.shellcheck.net/

Helpers

• Usefull functions

  appname=${0##*/}
  
  error_exit()
  {
      msg="$1"
      test "$msg" != "" || msg="an error occurred"
      printf "*** $msg\nabort...\n"
      exit 1
  }
  
  usage_exit()
  {
      echo "*** usage :"
      echo "$appname -opt1"
      echo "$appname -opt2 bla"
      echo "abort..."
      exit 1
  }
  
  ask_confirm()
  {
      while true; do
          read -p "$1" ret
          case $ret in
              [Yy]*)
                  return 0; break
              ;;
              [Nn]*)
                  return 1; break
              ;;
              *)
                  return 0; break
              ;;
          esac
      done
  }
  

Args

• Check number of arguments

  https://stackoverflow.com/questions/18568706/

  test "$#" -eq 1 || error_exit "Illegal number of parameters"

• Parsing args

  https://stackoverflow.com/questions/192249/

  #!/usr/bin/bash
  
  opt_param=0
  opt_filepath=""
  
  while (($#)); do
      case "$1" in
          -param)
          opt_param=1
          ;;
          -i)
              test $# -gt 1 || error_exit "*** missing option"
              shift
              opt_filepath="$1"
          ;;
          *)
          opt_param=0
          ;;
      esac
      shift
  done
  
  if [[ $opt_param == 1 ]]; then
      echo ok
  fi
  
  

Directories

• Script directory

  https://stackoverflow.com/questions/59895/

  basedir="$(dirname -- "$(readlink -f -- "$0";)")"

• Parse sub directories

  #!/usr/bin/bash
  
  for dir in $PWD/*; do
      if [[ -d $dir ]]; then
          echo $dir
      fi
  done
  

Files

• Test file extension

  https://stackoverflow.com/questions/21425006/

  #!/bin/bash
  
  inpath="file.html"
  
  if [[ "${inpath: -5}" == ".html" ]];then
      echo ok
  fi
  

• Change file extension

  https://stackoverflow.com/questions/1224766/

  inpath=file.md
  outpath=${inpath%.md}.html
  

• Heredoc

  https://linuxize.com/post/bash-heredoc/

  dest=~/test.txt
  sudo tee $dest > /dev/null << EOF
  bla
  ble
  blie
  EOF
  

• Output to file and stdout

  https://stackoverflow.com/questions/418896/

  program [arguments...] 2>&1 | tee -a "$outfile"
  

Misc

• Write functions

  https://linuxize.com/post/bash-functions/

• Checking sudo

  https://stackoverflow.com/questions/42875809/

  if [[ "$EUID" = 0 ]]; then
      echo "(1) already root"
  else
      sudo -k # make sure to ask for password on next sudo
      if sudo true; then
          echo "(2) correct password"
      else
          echo "(3) wrong password"
          exit 1
      fi
  fi