What does -z mean in Bash?

Bash

Bash Problem Overview

I'm looking at the following code:

if [ -z $2 ]; then
        echo "usage: ...

(The 3 dots are irrelevant usage details.)
Maybe I'm googling it wrong, but I couldn't find an explanation for the -z option.

Bash Solutions

Solution 1 - Bash

-z string True if the string is null (an empty string)

Solution 2 - Bash

-z

string is null, that is, has zero length

String=''   # Zero-length ("null") string variable.

if [ -z "$String" ]
then
  echo "\$String is null."
else
  echo "\$String is NOT null."
fi     # $String is null.

Solution 3 - Bash

test -z returns true if the parameter is empty (see man sh or man test).

Solution 4 - Bash

The expression -z string is true if the length of string is zero.

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Content TypeOriginal AuthorOriginal Content on Stackoverflow
QuestionNoichView Question on Stackoverflow
Solution 1 - BashYu HaoView Answer on Stackoverflow
Solution 2 - Bashuser2659589View Answer on Stackoverflow
Solution 3 - BashknittlView Answer on Stackoverflow
Solution 4 - BashmohitView Answer on Stackoverflow