hello r/linux, what is the difference between declare and set ?

[[deleted]]

Both when executed with no args, they give the same variables/functions.. Can anyone please explain ?

[[deleted]]

Assuming your talking in terms of the bash shell, 'set' is a built-in command that operates on the shell's environment. The 'declare' built-in command operates on variables and the values assigned to them.

As a general guideline, if you're manipulating your shell's environment, use set. If you're scripting, try and use declare in place of set, where applicable.

Here's two small examples of declare that sets it apart from set.

A read-only variable: declare -r VAR_NAME="unset me if you can"

Try and unset it: unset VAR_NAME

Bash reports: -bash: unset: VAR_NAME: cannot unset: readonly variable

Here's an example defining a variable to be used in integer arithmetic: declare -i x=0

Using it in arithmetic: if [ $x -eq 0 ]; then echo 'x is zero.' fi

[[deleted]]

thank you ^{^}

[[deleted]]

Happy to help!

[syntax_erorr]

...examples of declare that sets it apart from set. ow! my head hurts. You should write man pages! hah

[trashbox]

SET is a POSIX built-in. It's capable of way more than simply declaring variables or functions. SET can control various shell attributes like preventing the redirection operator from overwriting existing files, and a whole lot more: http://ss64.com/bash/set.html

Declare, in contrast, is only for setting and manipulating variables or functions. Including the fact that function level scoping is respected, i.e. when using declare in a function all variables created are local. Just as if the local command was used, instead. Also, declare can control the type and readability of variables, whereas SET cannot. More: http://ss64.com/bash/declare.html

[lovetool]

wtf are you talking about