For UNIX experts, and for those who have read my tutorial pages carefully, here are a few tests. Even for the experienced, these are nice puzzles which require some time to think.
You have done some calculations with a program which outputs a series of numbers. The result was 120 integer numbers printed in one line, separated by commas which immediately follow the numbers and an arbitrary amount of spaces and tab characters after the comma. You have redirected the output to a file and opened it with emacs. How many key presses do you need to modify the file so that the numbers are placed on separate lines and no trailing commas or white space are present? (Pressing a key together with a modifier key counts as one keypress.)
Use sed, that Turing machine of text processing, to swap the lines of a file pairwise. (Hint: use one of the GNU extensions for line addressing.) Can you also swap the first and third of every three lines?
Some free music sites allow you to listen to broadcasts with Realplayer or similar software which reads a playlist and plays files as they are downloaded. Can you use lynx (and some POSIX-conformant stuff ;) ) to download a specific file from the list? (There's no solution given for this one since it might allow you to dodge payment on some not-so-free sites. ;))) )
The command-line calculator bc allows to choose the base for the representation of numbers entered and output through the variables ibase and obase. What is the shortest way to set the output base equal to the input base?
Give a shell command line which prints out how many of the first 60 powers of two start with the digit 1, how many with 2, and so on up to 9.
