Question

In the following very simple ksh script example, I need to ask if func1 results equal to 4 ,

This is what I did in the example but this script does not print the “function result = 4” as I expected it to.

What do I need to change in the [[……]] in order to print the “function result = 4”

Remark – func1 must be in the [[…..]]

  #!/bin/ksh

  func1()
  {
    return 4
  }

  [[ ` func1 ` = ` echo $? `  ]]  && print "function result = 4"  

Answer 1

You need

#!/bin/ksh

  func1()
  {
    print -- 4
  }

  [[ $(func1) = 4  ]]  && print "function result = 4"  

OR

#!/bin/ksh

  func1()
  {
    return 4
  }

  func1 ; [[ $? == 4 ]]  && print "function result = 4"

There are several issues in the code that you present, so let me try to explain (You’re making it more complicated than it need be).

No. 1 is your use of back-ticks for command substitution, these have been deprecated in the ksh language since ~ 1995! Use $( … cmd ) for modern cmd-substitution. We often see backticks listed as a nod to portability, but only scripts written for systems where the Bourne shell is the only shell available require the use of backticks. (well, I don’t know about dash or ash, so maybe those too).

No 2. is that $? gets set after ever function or command or pipeline is executed and is the return code of that last command. It is a value between 0-255. When you have code like cmd ; rc=$? ; echo $? ; you’re now echoing the status of the assignment of rc=$? (which will almost always be 0), AND that is why you will see experienced scriptors save the value of $? before doing anything else with it.

Recall that command-substitution uses what ever is the output of the $( ... cmd ...) or backtics enclosed command while return sets the value of $? (until the very next command execution resets that value).

I hope this helps.