• BASH > cheatsheet 

      #!/usr/bin/env bash
NAME="John"
echo "Hello ${NAME}!"

      Shell execution

      echo "I'm in $(pwd)"

      Conditionals

      if [[ -z "$string" ]]; then
  echo "String is empty"
elif [[ -n "$string" ]]; then
  echo "String is not empty"
fi

      Brace expansion

      echo {A,B}.js

      {A,B} > A B {A,B}.js > A.js B.js {1..5} > 1 2 3 4 5   See: Brace expansion

      SUBSTITUTION

      name="John"
echo ${name/J/j}    > "john"
echo ${name:0:2}    > "Jo"
echo ${name::2}     > "Jo"
echo ${name::-1}    > "Joh"
echo ${name:(-1)}   > "n"
echo ${name:(-2):1} > "h"
echo ${food:-Cake}  > $food or "Cake"
      length=2 ; echo ${name:0:length} > "Jo"
      STR="/path/to/foo.cpp"
echo ${STR%.cpp}    # /path/to/foo
echo ${STR%.cpp}.o  # /path/to/foo.o
echo ${STR%/*}      # /path/to (dirpath)
echo ${STR##*.}     # cpp (extension)
echo ${STR##*/}     # foo.cpp (basepath)
echo ${STR#*/}      # path/to/foo.cpp
echo ${STR/foo/bar} # /path/to/bar.cpp
      STR="Hello world"
echo ${STR:6:5}   # "world"
echo ${STR: -5:5} # "world"

      ${FOO%suffix} Remove suffix ${FOO#prefix} Remove prefix ${FOO%%suffix} Remove long suffix ${FOO##prefix} Remove long prefix ${FOO/from/to} Replace first match ${FOO//from/to} Replace all ${FOO/%from/to} Replace suffix ${FOO/#from/to} Replace prefix

      Substrings

      ${FOO:0:3} Substring (position, length) ${FOO:(-3):3} Substring from the right

      Length

      ${#FOO} Length of $FOO

      Manipulation

      STR="HELLO WORLD!"
echo ${STR,}  > "hELLO WORLD!" (lowercase 1st letter)
echo ${STR,,} > "hello world!" (all lowercase)

STR="hello world!"
echo ${STR^}   #=> "Hello world!" (uppercase 1st letter)
echo ${STR^^}  #=> "HELLO WORLD!" (all uppercase)

      Default values

      ${FOO:-val} $FOO, or val if unset (or null) ${FOO:=val} Set $FOO to val if unset (or null) ${FOO:+val} val if $FOO is set (and not null) ${FOO:?message} Show error message and exit if $FOO is unset (or null)   Omitting the : removes the (non)nullity checks, e.g. ${FOO-val} expands to val if unset otherwise $FOO.

      Loops

      for i in /etc/rc.*; do
  echo $i
done
      for ((i = 0 ; i < 100 ; i++)); do
  echo $i
done
      for i in {1..5}; do
   echo "Welcome $i"
done
      for i in {5..50..5}; do
   echo "Welcome $i"
done

      Reading lines

      cat file.txt | while read line; do
  echo $line
done

      boucle infinie

      while true; do
  ···
done

      Fonctions

      get_name() {
  echo "John"
}
echo "You are $(get_name)"
      myfunc() {
    echo "hello $1"
}
      myfunc "John"

      Retour

      myfunc() {
    local myresult='some value'
    echo $myresult
}
      result="$(myfunc)"

      Raising errors

      myfunc() {
  return 1
}
      if myfunc; then
  echo "success"
else
  echo "failure"
fi

      Arguments

      $# Number of arguments $* All positional arguments (as a single word) $@ All positional arguments (as separate strings) $1 First argument $_ Last argument of the previous command   Note: $@ and $* must be quoted in order to perform as described. Otherwise, they do exactly the same thing (arguments as separate strings).

      Conditions

      [[ -z STRING ]]	Empty string
      [[ -n STRING ]]	Not empty string
      [[ STRING == STRING ]]	Equal
      [[ STRING != STRING ]]	Not Equal
      [[ NUM -eq NUM ]]	Equal
      [[ NUM -ne NUM ]]	Not equal
      [[ NUM -lt NUM ]]	Less than
      [[ NUM -le NUM ]]	Less than or equal
      [[ NUM -gt NUM ]]	Greater than
      [[ NUM -ge NUM ]]	Greater than or equal
      [[ STRING =~ STRING ]]	Regexp
      (( NUM < NUM ))	Numeric conditions
      [[ -o noclobber ]]	If OPTIONNAME is enabled
      [[ ! EXPR ]]	Not
      [[ X && Y ]]	And
      [[ X || Y ]]	Or

      File conditions

      [[ -e FILE ]]	Exists
      [[ -r FILE ]]	Readable
      [[ -h FILE ]]	Symlink
      [[ -d FILE ]]	Directory
      [[ -w FILE ]]	Writable
      [[ -s FILE ]]	Size is > 0 bytes
      [[ -f FILE ]]	File
      [[ -x FILE ]]	Executable
      [[ FILE1 -nt FILE2 ]]	1 is more recent than 2
      [[ FILE1 -ot FILE2 ]]	2 is more recent than 1
      [[ FILE1 -ef FILE2 ]]	Same files

      Example

      if [[ -z "$string" ]]; then
  echo "String is empty"
elif [[ -n "$string" ]]; then
  echo "String is not empty"
else
  echo "This never happens"
fi
      # Combinations
if [[ X && Y ]]; then
  ...
fi
      # Equal
if [[ "$A" == "$B" ]]
      # Regex
if [[ "A" =~ . ]]
      if (( $a < $b )); then
   echo "$a is smaller than $b"
fi
      if [[ -e "file.txt" ]]; then
  echo "file exists"
fi

      Arrays

      Fruits=('Apple' 'Banana' 'Orange')
      Fruits[1]="Banana"

      Working with arrays

      echo ${Fruits[-1]}     # Last element
echo ${Fruits[@]}      # All elements, space-separated
echo ${#Fruits[@]}     # Number of elements
echo ${#Fruits}        # String length of the 1st element
echo ${#Fruits[3]}     # String length of the Nth element
echo ${Fruits[@]:3:2}  # Range (from position 3, length 2)
echo ${!Fruits[@]}     # Keys of all elements, space-separated

      Operations

      Fruits=("${Fruits[@]}" "Watermelon")    # Push
Fruits+=('Watermelon')                  # Also Push
Fruits=( ${Fruits[@]/Ap*/} )            # Remove by regex match
unset Fruits[2]                         # Remove one item
Fruits=("${Fruits[@]}")                 # Duplicate
Fruits=("${Fruits[@]}" "${Veggies[@]}") # Concatenate
lines=(`cat "logfile"`)                 # Read from file

      Iteration

      for i in "${arrayName[@]}"; do
  echo $i
done

      Dictionaries

      declare -A sounds
      sounds[dog]="bark"
sounds[cow]="moo"
sounds[bird]="tweet"
sounds[wolf]="howl"
      echo ${sounds[dog]} # Dog's sound
echo ${sounds[@]}   # All values
echo ${!sounds[@]}  # All keys
echo ${#sounds[@]}  # Number of elements
unset sounds[dog]   # Delete dog
      for val in "${sounds[@]}"; do
  echo $val
done

      Iterate over keys

      for key in "${!sounds[@]}"; do
  echo $key
done

      History

      Commands

      history Show history
      shopt -s histverify Don’t execute expanded result immediately

      Expansions

      !$ Expand last parameter of most recent command
      !* Expand all parameters of most recent command
      !-n Expand nth most recent command
      !n Expand nth command in history
      !<command> Expand most recent invocation of command <command>

      Operations

      !! Execute last command again
      !!:s/<FROM>/<TO>/ Replace first occurrence of <FROM> to <TO> in most recent command
      !!:gs/<FROM>/<TO>/ Replace all occurrences of <FROM> to <TO> in most recent command
      !$:t Expand only basename from last parameter of most recent command
      !$:h Expand only directory from last parameter of most recent command

      !! and !$ can be replaced with any valid expansion.

      Slices

      !!:n Expand only nth token from most recent command (command is 0; first argument is 1)
      !^ Expand first argument from most recent command
      !$ Expand last token from most recent command
      !!:n-m Expand range of tokens from most recent command
      !!:n-$ Expand nth token to last from most recent command

      !! can be replaced with any valid expansion i.e. !cat, !-2, !42, etc.

      Miscellaneous

      Numeric calculations

      $((a + 200))      # Add 200 to $a
      $(($RANDOM%200))  # Random number 0..199

      Subshells

      (cd somedir; echo "I'm now in $PWD")
pwd # still in first directory

      Redirection

      python hello.py > output.txt   # stdout to (file)
python hello.py >> output.txt  # stdout to (file), append
python hello.py 2> error.log   # stderr to (file)
python hello.py 2>&1           # stderr to stdout
python hello.py 2>/dev/null    # stderr to (null)
python hello.py &>/dev/null    # stdout and stderr to (null)
      python hello.py < foo.txt      # feed foo.txt to stdin for python
diff <(ls -r) <(ls)            # Compare two stdout without files

      Inspecting commands

      command -V cd
#=> "cd is a function/alias/whatever"

      Trap errors

      trap 'echo Error at about $LINENO' ERR

      or

      traperr() {
  echo "ERROR: ${BASH_SOURCE[1]} at about ${BASH_LINENO[0]}"
}

set -o errtrace
trap traperr ERR

      Case/switch

      case "$1" in
  start | up)
    vagrant up
    ;;
  *)
    echo "Usage: $0 {start|stop|ssh}"
    ;;
esac

      Source relative

      source "${0%/*}/../share/foo.sh"

      printf

      printf "Hello %s, I'm %s" Sven Olga
#=> "Hello Sven, I'm Olga

printf "1 + 1 = %d" 2
#=> "1 + 1 = 2"

printf "This is how you print a float: %f" 2
#=> "This is how you print a float: 2.000000"

      Transform strings

      -c Operations apply to characters not in the given set
      -d Delete characters
      -s Replaces repeated characters with single occurrence
      -t Truncates
      [:upper:] All upper case letters
      [:lower:] All lower case letters
      [:digit:] All digits
      [:space:] All whitespace
      [:alpha:] All letters
      [:alnum:] All letters and digits

      Example

      echo "Welcome To Devhints" | tr [:lower:] [:upper:]
WELCOME TO DEVHINTS

      Directory of script

      DIR="${0%/*}"

      Getting options

      while [[ "$1" =~ ^- && ! "$1" == "--" ]]; do case $1 in
  -V | --version )
    echo $version
    exit
    ;;
  -s | --string )
    shift; string=$1
    ;;
  -f | --flag )
    flag=1
    ;;
esac; shift; done
if [[ "$1" == '--' ]]; then shift; fi

      Heredoc

      cat <<END
hello world
END

      Reading input

      echo -n "Proceed? [y/n]: "
read ans
echo $ans
      read -n 1 ans    # Just one character

      Special variables

      $? Exit status of last task
      $! PID of last background task
      $$ PID of shell
      $0 Filename of the shell script
      $_ Last argument of the previous command

      Go to previous directory

      pwd # /home/user/foo
cd bar/
pwd # /home/user/foo/bar
cd -
pwd # /home/user/foo

      Check for command’s result

      if ping -c 1 google.com; then
  echo "It appears you have a working internet connection"
fi

      Grep check

      if grep -q 'foo' ~/.bash_history; then
  echo "You appear to have typed 'foo' in the past"
fi

      VOIR AUSSI

 

Aucun commentaire

 

Laissez un commentaire