[SOLVED] What condition is this checking for: if [ -z $1 ]

Issue

I have three if conditions in a shell script I have been given, can I be assisted with what they each mean in English. Also, how would I use the man pages to find out similar commands in the future?

The conditions are as follows:

1. if [ -z $1 ]

2. if [ ! -r $1 ]

3. if [ -n $3 ]

Solution

The trick here is that [ is not punctuation, but the name of a command, which is also called test. So the help page you need is man test.

On that page, you can see the options listed:

   -z STRING
          the length of STRING is zero

   ! EXPRESSION
          EXPRESSION is false

   -r FILE
          FILE exists and read permission is granted

   -n STRING
          the length of STRING is nonzero

Since bash includes a built-in implementation of this command, you can also find the information under man bash and in the bash reference manual.

Answered By - IMSoP