밴쿠버 코로노의 개발일지

https://gist.github.com/vratiu/9780109

$ __msg = "message"
$ echo -e "\033[0;31m${__msg}\033[0m"

declare: declare [-afFirtx] [-p] [name[=value] ...]

Declare variables and/or give them attributes. If no NAMEs are given, then display the values of variables instead. The -p option will display the attributes and values of each NAME.

The flags are:
       -a to make NAMEs arrays (if supported)
       -f to select from among function names only
       -F to display function names (and line number and source file name if debugging) without definitions.  
       -i to make NAMEs have the `integer' attribute.
       -r to make NAMEs readonly
       -t to make NAMEs have the `trace' attribute
      -x to make NAMEs export.

Variables with the integer attribute have arithmetic evaluation (see `let') done when the variable is assigned to.

When displaying values of variables, -f displays a function's name and definition. The -F option restricts the display. to function name only.

Using `+' instead of `-' turns off the given attribute instead. When used in a function, makes NAMEs local, as with the `local' command.

bash script의 Variable의 경우 보통 type 없이 생성하고 사용한다. 하지만 declare로 선언할 경우 type과 접근권한을 설정해줄 수 있다. 

-a : Array

$ declare -a os_name=(Ubuntu Mint Kubuntu lubuntu Debian)
$ echo ${os_name[@]}
$ declare -A os_family
$ os_family["Redhat"]="Fedora"
$ os_family["Arch"]="Manjaro"
$ os_family["Debian"]="Ubuntu"
$ echo ${os_family[@]}

-f : Select Function name

$ function hello_world(){ echo "Linux Geeks"; }
$ declare -f hello_world                                                                                  SIGINT(2) ↵  108  15:53:10 
hello_world () {
	echo "Linux Geeks"
}

-i : Integer attribute

$ declare -i num=10
$ echo $num
10

-x : Export attribute

$ declare -x name=declareTest
$ sh -c “echo $name”
declareTest

-r : Readonly attribute

$ declare -r num=10
$ num=11
-bash: no: readonly variable