is-null
)Checks if a variable is null or undefined
is-null
checks if a variable is null or undefined. If multiple variables are passed in is-null
’s parameters, the exit number will be a count of the number of non-null variables checked.
is-null
is intended to be run non-interactively, where it doesn’t write to stdout but instead communicates its results via exit number. However if stdout is a TTY is-null
will additionally write to the terminal.
The following conditions are considered “null” by is-null
:
null
or a value of null.Zero length strings, strings containing the word “null” and numeric data types (eg num
, int
, float
with the value of 0
) are all not null.
is-null variable_name... -> <stdout>
» $baz = ""
» is-null foo bar baz
foo: undefined or null
bar: undefined or null
baz: defined and not null
if { is-null foobar } then {
out "baz is undefined"
}
export
): Define an environmental variable and set it’s valueglobal
): Define a global variable and set it’s valueset
): Define a variable (typically local) and set it’s value??
Null Coalescing Operator: Returns the right operand if the left operand is empty / undefined (expression)This document was generated from builtins/core/typemgmt/isnull_doc.yaml.
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