Test binary operator expected
Any time one of the test pathname operator test binary operator expected fails, be accurate in your error message. There are many ways to make mistakes in script programming. With one argument and no operators, the test command returns success if the argument is not the empty string test -n 1. First, let me say there is nothing wrong with line 3. The first type simply announces that you have reached a certain point in the program.
The above syntactic-sugar line is equivalent to this also incorrect line: These errors can be a real test binary operator expected to find in a long script. Here we have another case of a mistake in one line causing a problem later in the script. The test command is defaulting to use an implied -n operator on the left. We saw this in our earlier discussion on stubbing.
These are all correct opposites. Be sure to enter it exactly as written. This brings up an important thing to test binary operator expected when you are writing your scripts. To do this, add a " -x " to the first line of your script, like this:. Running the script using a shell with the debug options -x or -v set may also be helpful:.
So what's wrong with line 5? If you want to perform equality tests, you must separate each argument by blanks so that test sees three separate arguments, not just one: To do this, create the following test binary operator expected called trouble.
Rather than using the test command twice, you can simply join them into one using the correct test Boolean operator:. You can confirm the validity of this by trying it on the command line: Here are two identical mistakes: This next test binary operator expected fails because of the missing blank before the required closing square bracket: The correct shell scripting form does not use the redirection syntax:
Split the huge condition into more readable error messages. The following code does not work; because, blanks are missing around the first square bracket, making it into an unknown command named [1: The string 1 is never empty, so the above test, and the if test binary operator expected, always succeeds. This technique is called tracing.
What happens is the shell keeps looking test binary operator expected the closing quotation mark to tell it where the end of the string is, but runs into the end of the file before it finds it. If you combine test binary operator expected negation operator of test with the shell return code negation operator mentioned earlier that also uses! The command name after the ifabove, is test. By doing this, you can isolate which part of a program is causing or not causing a problem.
Use echo commands to verify your assumptions. Always use blanks around [ and ]: Test binary operator expected can confirm the validity of this by trying it on the command line: Now, when you run your script, bash will display each line with expansions performed as it executes it. When you run this script, it should output the line "Number equals 1" because, well, number equals 1.