nice_things/macros/var.macro.sh

var

Since 0.3.0 · Source

Synopsis
#{{{ var <assignee>=<assignor> [<assignee>=<assignor>]… }}}

Configuration
–

Description
Use indirection to dynamically assign variables.

No validation checks are done at run-time, which makes the code printed by this macro much faster than invoking the assign_variable function, but unsafe to use on untrusted inputs.

Three forms of <assignee> can be used:

• mandatory: The default; simply use the name of a variable or positional parameter as <assignee>. Will abort at run-time if <assignee> is null.
• optional: Append a question mark ? to the <assignee> name: <assignee>?=<assignor>; Will do nothing if <assignee> is null at run-time.
• explicit: Write your own parameter expansion in the <assignee> position, implementing whatever rules you want. For advanced use-cases, like dynamic buckets in a data structure.

Options
–

Operands

• <assignee>: Variable or positional parameter containing the name of the variable to be assigned.
• <assignor>: Variable or positional parameter holding the value to assign.

Stdin
–

Stdout
One line of code is printed.

Stderr
–

Exit status
0: Successful completion.

Abort
Aborts if <assignee> is null.

Usage examples

# Assign the result of a function to the <out_var> parameter
#{{{
var 1=result
#}}}

# Assign the result of a function to an optional <out_var> parameter
#{{{
var '1?=result'
#}}}

# Example taken from Array_bucket_set_
# Assign values to arbitrary variable name expansions
#{{{
# shellcheck disable=SC2016
var 'NS__bucket_${1:?}__${2:?}=${3}' \
	'NS__bucket_${1}__${2}_len=${4}'
#}}}