## To build: ``` make all ``` There is another version which is the original entry. See [Alternate code](#alternate-code) for details as to how to use and why it was made the alt version. ## To use: ``` ./clock1.sh ./clock2.sh ./clock3.sh ``` ## Try: ``` ./try.sh ``` ## Alternate code: The original version had a display problem in modern systems which somewhat affected the usability of the program. This alternate code, the original, is provided, to show the differences. ### Alternate build: ``` make alt ``` ### Alternate try: ``` ./try.alt.sh ``` ## Judges' remarks: Time and time again, Brian Westley seems to come up with a winning entry! We are amazed at how much is being done with only one relatively short line. We think you will as well if you take the time to understand it. ## Author's remarks: This 1-line program allows various analog ASCII clocks to print out the time; the ASCII clock is built from the command line arguments, so many different types of clocks can be generated. Three different scripts are supplied to print out a grandfather clock, a mantle clock that runs backwards, and a linear-style clock. (they are [clock1.sh](%%REPO_URL%%/1996/westley/clock1.sh), [clock2.sh](%%REPO_URL%%/1996/westley/clock2.sh), and [clock3.sh](%%REPO_URL%%/1996/westley/clock3.sh). The program makes the following (possibly non-portable) assumptions: 1. Command line strings can be written to. 2. `argv[0]` can be written to as if it were a `long *`. 3. The first three elements of the `struct *` returned by `localtime(3)` are seconds, minutes, hours, and all are `int`s. 4. My sample scripts assume ASCII, though this is not inherent in the code, just my sample scripts. These assumptions are pretty reasonable. 2) can be eliminated but makes the code larger. The code is simple; the arguments passed are: ``` ./westley minute_map hour_map hand_symbol clock_image ``` The program merely takes the minute (0-59) and the hour (0-23) values, looks up the offsets in `minute_map` and `hour_map` and writes the `hand_symbol` for each into the `clock_image` string. This string is then printed. The `for()` loop starts by calling `time()` with `argv[0]`, so the time value (a `long`) is written into the program name. The `for()` control value is `argc`, which starts at `5`, but the `/=2` statement is executed before the test, so the `for()` loop is executed twice, with `h=2`, then `h=1` (for hour & minute). The statement of the `for()` loop takes the hour or minute field of the struct returned by `localtime(3)` by casting it to an `int *` and dereferencing element `[h]`. It is slightly smaller to use the trick `h[(int*)localtime(*m)]` instead of `((int*)localtime(*m))[h]`. This value is in turn indexed into the `hour_map` or `minute_map` parameter to determine where the 'hand' symbol should be written into the `clock_image`. Note that the hands move in a quantum fashion; 3:59 looks deceptively like 2:59, since the hour hand will be at the 3 position. It won't move until both hands click over at 4:00.