Well, I addressed several basic rules, now let's see what the test-command can do for you. With one parameter, it defaults to the -n test: It tests if a provided string is empty ( FALSE) or not ( TRUE) - due to the lack of spaces to separate the arguments the shown command always ends TRUE! This provides exactly one test-argument to the command. Don't give a glob (filename-wildcards) as it can expand to many filenames ⇒ too many arguments!Īnother common mistake is to provide too few arguments: Please also note that the file-tests want one filename to test. Since we call a normal ordinary command ('test' or '[') the shell will word-split the expansion of the variable mymusic: You need to quote it when you don't want the test-command to complain about too many arguments for this test-type! If you didn't understand it, please read the article about words. Mymusic='/data/music/Van Halen/Van Halen - Right Now.mp3'Īs you definitely noted, the filename contains spaces. Let's check for some of your music files:

One might think now that these '' belong to the syntax of Bash's if-clause: No they don't! It's a simple, ordinary command, still!Īnother thing you have to remember is that if the test command wants one parameter for a test, you have to give it one parameter. Let's rewrite the above example to use it: There's a second standardized command that does exactly the same: the command ' ': It forms ' ' Usually it's the command name ' test' followed by a test type (here ' -e' for 'file exists') followed by test-type-specific values (here the filename to check, ' /etc/passwd'). The syntax of the test command is relatively easy. Using this exit code, it's possible to let Bash react on the result of such a test, here by using the command in an if-statement: This command allows you to do various tests and sets its exit code to 0 ( TRUE) or 1 ( FALSE) whenever such a test succeeds or not.

Ksh if test zero byte file