Dart
Dart
HTML Canvas
HTML Canvas
Redis
Redis
Bash
Bash
JavaScript
JavaScript
Bash
Bash

Getting Started

Shell execution

# => I'm in /path/of/current
echo "I'm in $(PWD)"
# Same as:
echo "I'm in `pwd`"

See: Command substitution

Brace expansion

echo {A,B}.js
Expression Description
{A,B} Same as A B
{A,B}.js Same as A.js B.js
{1..5} Same as 1 2 3 4 5
See: Brace expansion

Conditionals

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

See: Conditionals

Functions

get\_name() {
    echo "John"
}
echo "You are $(get\_name)"

See: Functions

Arguments

Expression Description
$1 … $9 Parameter 1 … 9
$0 Name of the script itself
$1 First argument
${10} Positional parameter 10
$# Number of arguments
$$ Process id of the shell
$* All arguments
$@ All arguments, starting from first
$- Current options
$_ Last argument of the previous command
See: Special parameters

Comments

# This is an inline Bash comment.

: '
This is a
very neat comment
in bash
'

Multi-line comments use :' to open and ' to close

Variables

NAME="John"
echo ${NAME}    # => John (Variables)
echo $NAME      # => John (Variables)
echo "$NAME"    # => John (Variables)
echo '$NAME'    # => $NAME (Exact string)
echo "${NAME}!" # => John! (Variables)
NAME = "John"   # => Error (about space)

hello.sh

#!/bin/bash
VAR="world"
echo "Hello $VAR!" # => Hello world!

Execute the script

$ bash hello.sh
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