[15] Make a program that takes a list of files named on the command line and reports for each one whether it's readable, writable, executable, or doesn't exist. (Hint: It may be helpful to have a function that will do all of the file tests for one file at a time.) What does it report about a file which has been chmod'ed to 0? (That is, if you're on a Unix system, use the command chmod 0some_file to mark that file as neither being readable, writable, nor executable.) In most shells, use a star as the argument to mean all of the normal files in the current directory. That is, you could type something like ./ex11-1 * to ask the program for the attributes of many files at once.
