Bash/Shell Programming – Binary Operator Expected

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I'm working on cleaning up our licensing for Parallels as we have a few different license keys that have been used over the years. I'm trying to build an Extension Attribute that either provides me the key or tell me it's "wrong". If it doesn't have the correct key, this line either won't exist or the key will be something other than "PDEI". I'm a total rookie at scripting so what I've put together is purely by piecing together other scripts with a whole lot of trial and error.

Here is what I've come up with so far. This is the error I get on a machine with the correct key: This is the error I get on a machine with an incorrect key: I would be truly greatfull if anyone is able to help me clean this up or has an easier way to do this. The error messages are telling you what the issue is.

You're trying to equate a key with alpha and digits in it to "0". Essentially, you're asking the shell to do a math operation on something that is actually not a number. Were you trying to test for a null value perhaps? You can do a few things here to correct this. If you're certain that a correct key will have "PDEI" as part of the string, and an incorrect one will never have that, you can try using a "like" operator instead.

That would tell it to evaluate the string returned to see if "PDEI" is part of it somewhere. You can probably also check for a null value, but you mentioned that its possible an incorrect key may exist, in which case testing for null isn't going to be as accurate, I think.

I don't use Parallels, so I'm taking guesses here. I have no idea how the licensing keys are set up. Thanks for the post. Your explanation is easier to understand that some of the 'man' pages I've tried to interpret. Again, it's all quite new to me. From there I can scope a Smart Group to determine if the key is right or not. I would rather have something returned so I can scope the Smart Group to look for that as opposed to using the "is not like".

Not a real big deal though. I guess I do have one last question this is for my own knowledge. Is there a way to have the command only include the PDEI. My mistake on not explaining one additional thing.

Give it a try with the double brackets. The single brackets will give you the 'binary operator expected' error you saw. I actually make it a habit of using double brackets for nearly all evaluation stuff in scripts. There are far fewer instances where single brackets works than when it fails. For example, if the string that gets returned is: As always there are probably 6 other ways you can do it. I really appreciate your explanations as well. I owe you a beverage if we ever meet.

I was gonna mention awk's regex matching as well, but didn't want to throw too much info at him at once: Dialog with your fellow IT professionals, gain insight about Apple device deployments, share best practices and bounce ideas off each other. Learn more about Jamf. Parallels script help Posted: Parallels Desktop 7 for Mac.

Most Likes Oldest Newest. Thanks again for your help. Also, you almost never need to chain a grep and awk or sed. Log in to post a response. Spam This is an advertisement—it is not useful or relevant.

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There are many ways to make mistakes in script programming. Here are some warnings about common errors. Shells are not particularly good about giving helpful error messages when shell scripts contain errors. For example, having a missing or non-integer argument to the test command may produce a vague error message:.

A common mistake when writing a new shell script is to write too many lines of code, run the new script, and then get too many error messages. Create shell scripts a few lines at a time, testing the script after you add each line or two so you know where the errors lie. Running the script using a shell with the debug options -x or -v set may also be helpful:.

They find and run commands, and it is commands that you must use in if statements. The error message bash: The shell if keyword must always be followed by a Unix command name.

Always remember to code some Unix command name after if:. The command name after the if , above, is test. If you want to test the return status of grep , grep must be the command name that immediately follows the if keyword:. The if keyword must always be followed by a command name, and that command name is exactly one square bracket [ in the syntactic-sugar form of the test helper command.

The following code does not work; because, blanks are missing around the first square bracket, making it into an unknown command named [ The shell sees [1 and [! The following incorrect statement fails for the same reason:. The arguments to the test command must always be separate command line arguments. This next line fails because of the missing blank before the required closing square bracket:.

The corrected line uses blanks:. The test helper command behaves differently depending on the number of arguments you pass to it:. If the test command has only one single command line argument, it defaults to using -n as the implied operator test for non-empty string on the one argument.

The following one-argument tests are always TRUE, though they may not appear that way at first to human eyes:. In all the above lines, the test command has only one command line argument not counting the trailing ] that is always ignored. Since the single argument to test is not the empty string, test returns a good status and the if succeeds.

The test command is defaulting to use an implied -n operator on the left. The shell is actually executing these tests:. If you want to perform equality tests, you must separate each argument by blanks so that test sees three separate arguments, not just one:.

Here are two identical mistakes:. The test command produces no output; the file remains empty. The test command itself is left with only one single command line argument, the digit 1. With one argument and no operators, the test command returns success if the argument is not the empty string test -n 1. The string 1 is never empty, so the above test, and the if , always succeeds. The exit status negation operator! The test command uses the exclamation point operator!

If you combine the negation operator of test with the shell return code negation operator mentioned earlier that also uses! Rework the expression to use only a single! To test if a file is non-existent or exits but is not readable:. The shell return code negation operator! You cannot use them inside test expressions. Use -a and -o to separate Boolean clauses to the test command:. Above, the separates two different and complete test command executions. Rather than using the test command twice, you can simply join them into one using the correct test Boolean operator:.

The test helper command has six ways to compare numbers and two ways to compare strings. Boolan logic has some subtle consequences when applied to the operations performed by the test helper command. These are all correct opposites. The logical opposite of the test operator -lt less than is not -gt greater than , it is -ge greater than or equal to.

If you are not younger than your sister, you are either older or the same age. The opposite of the test operator -gt is not -lt , it is -le. The test operators -f and -d are not opposites. If a pathname is not a file, it may or may not be a directory. It could be a directory or any number of other special file types under Unix.

The test pathname operators all return success zero only if the pathname is accessible all the directories can be traversed AND the pathname exists AND if it has the given pathname property. You need to apply more programming logic if you want to know that a pathname actually exists but is not, for example, readable:.

Remember that inverting a pathname test may mean the inverted test succeeds because the pathname is not accessible or does not exist! If a test pathname operator e. Without first testing if you can access the pathname and that it actually exists, the following error message is misleading:.

While it is true that the pathname is not readable, the above error message is incomplete. You might not have permission to traverse all the directories in its pathname, or, the pathname might not even exist. Saying the overall pathname is not readable is true, but it is only part of the truth. A more accurate error message would be:. If you want to be more specific in your error message about why the pathname is not readable, you need code to test for existence first:.

The test for readability is now done only if the pathname exists and is accessible; if the test for readability fails, you know the existing, accessible pathname item is truly not readable. The error message is more accurate now. Any time one of the test pathname operator tests fails, be accurate in your error message. State whether the failure is due to a missing or inaccessible pathname, or due to a failure of the actual test being performed on the existing, accessible pathname.

Be careful in if statements when testing multiple conditions at the same time that you do not make the failure error message unhelpful:. The error would have to read like this: Which failure was it?

Such a complex error message is not helpful to the users of your scripts! The programmer forgot that the if statement can directly test the return code of the command it executes. Calling up the test command to examine the shell variable for the return code of the previous command is superfluous. Plain Text - plain text version of this page in Pandoc Markdown format. Shell Script Problems — arithmetic, syntax, test, boolean, etc. Allen — idallen idallen. For example, having a missing or non-integer argument to the test command may produce a vague error message: Running the script using a shell with the debug options -x or -v set may also be helpful: This line below is wrong thinking; it forgets to use the test helper program: Always remember to code some Unix command name after if: The above syntactic-sugar line is equivalent to this also incorrect line: If you want to test the return status of grep , grep must be the command name that immediately follows the if keyword: The following code does not work; because, blanks are missing around the first square bracket, making it into an unknown command named [1: The following incorrect statement fails for the same reason: Always use blanks around [ and ]: This next line fails because of the missing blank before the required closing square bracket: The corrected line uses blanks: The following one-argument tests are always TRUE, though they may not appear that way at first to human eyes: The shell is actually executing these tests: If you want to perform equality tests, you must separate each argument by blanks so that test sees three separate arguments, not just one: Here are two identical mistakes: The correct shell scripting form does not use the redirection syntax: These script command lines below have a single empty or null string argument: To test if a file is non-existent or exits but is not readable: Use -a and -o to separate Boolean clauses to the test command: Rather than using the test command twice, you can simply join them into one using the correct test Boolean operator: You cannot replace the test!

You need to apply more programming logic if you want to know that a pathname actually exists but is not, for example, readable: Without first testing if you can access the pathname and that it actually exists, the following error message is misleading: A more accurate error message would be: