#!/usr/bin/env bash

NAME="John"
echo "Hello $NAME!"

NAME="John"
echo $NAME
echo "$NAME"
echo "${NAME}!"

NAME="John"
echo "Hi $NAME"  #=> Hi John
echo 'Hi $NAME'  #=> Hi $NAME

echo "I'm in $(pwd)"
echo "I'm in `pwd`"
# Same

git commit && git push
git commit || echo "Commit failed"

get_name() {
  echo "John"
}

echo "You are $(get_name)"

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

set -euo pipefail
IFS=$'\n\t'

echo {A,B}.js
{A,B}	#Same as A B
{A,B}.js	#Same as A.js B.js
{1..5}	#Same as 1 2 3 4 5

name="John"
echo ${name}
echo ${name/J/j}    #=> "john" (substitution)
echo ${name:0:2}    #=> "Jo" (slicing)
echo ${name::2}     #=> "Jo" (slicing)
echo ${name::-1}    #=> "Joh" (slicing)
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##*.}     # cpp (extension)
echo ${STR##*/}     # foo.cpp (basepath)

echo ${STR#*/}      # path/to/foo.cpp
echo ${STR##*/}     # foo.cpp

echo ${STR/foo/bar} # /path/to/bar.cpp
STR="Hello world"
echo ${STR:6:5}   # "world"
echo ${STR:-5:5}  # "world"
SRC="/path/to/foo.cpp"
BASE=${SRC##*/}   #=> "foo.cpp" (basepath)
DIR=${SRC%$BASE}  #=> "/path/to/" (dirpath)

${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

# Single line comment
: '
This is a
multi line
comment
'

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

${#FOO}	#Length of $FOO

${FOO:-val}	#$FOO, or val if not set
${FOO:=val}	#Set $FOO to val if not set
${FOO:+val}	#val if $FOO is set
${FOO:?message}	#Show error message and exit if $FOO is not set
#The : is optional (eg, ${FOO=word} works)

for i in /etc/rc.*; do
  echo $i
done

for i in {1..5}; do
    echo "Welcome $i"
done
# With step size
for i in {5..50..5}; do
    echo "Welcome $i"
done

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

while true; do
  ···
done

myfunc() {
    echo "hello $1"
}
# Same as above (alternate syntax)
function myfunc() {
    echo "hello $1"
}
myfunc "John"

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

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

$#	#Number of arguments
$*	#All arguments
$@	#All arguments, starting from first
$1	#First argument

[ STRING = STRING ]	#Equal
[ STRING != STRING ]	#Not Equal
[ -z STRING ]	#Empty string
[ -n STRING ]	#Not empty string
[ 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

[ -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

# String
if [ -z "$string" ]; then
  echo "String is empty"
elif [ -n "$string" ]; then
  echo "String is not empty"
fi
# Combinations
if [ X ] && [ Y ]; then
  ...
fi
# Equal
if [[ "$A" == "$B" ]]
# Regex
if [[ "A" =~ "." ]]
if (( $a < $b ))
if [ -e "file.txt" ]; then
  echo "file exists"
fi

Fruits=('Apple' 'Banana' 'Orange')
Fruits[0]="Apple"
Fruits[1]="Banana"
Fruits[2]="Orange"

echo ${Fruits[0]}           # Element #0
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)

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

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

set -o noclobber  # Avoid overlay files (echo "hi" > foo)
set -o errexit    # Used to exit upon error, avoiding cascading errors
set -o pipefail   # Unveils hidden failures
set -o nounset    # Exposes unset variables

set -o nullglob    # Non-matching globs are removed  ('*.foo' => '')
set -o failglob    # Non-matching globs throw errors
set -o nocaseglob  # Case insensitive globs
set -o globdots    # Wildcards match dotfiles ("*.sh" => ".foo.sh")
set -o globstar    # Allow ** for recursive matches ('lib/**/*.rb' => 'lib/a/b/c.rb')

#Set GLOBIGNORE as a colon-separated list of patterns to be removed from glob matches.

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

!$	#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>

!!	#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.

!!: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.

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

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

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

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

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 "$1" in
  start | up)
    vagrant up
    ;;

  *)
    echo "Usage: $0 {start|stop|ssh}"
    ;;
esac

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

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

DIR="${0%/*}"

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

cat <<END
hello world
END

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

$?	#Exit status of last task
$!	#PID of last background task
$$	#PID of shell

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