I suppose smart equates to quirky in most programming circumstances. This maxim definitely holds true for the getopt() function. Before you can appreciate this function and put it to use, you must understand how it works and why it can be quirky.
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The challenge for last month’s Exercise was to generate a table showing a stock price updated every 30 minutes during the trading day. This month’s Exercise expands upon the process by having your code examine the stock price highs and lows and determine the greatest increase in stock value. This calculation means more than just finding the high and low values.
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The getopt() function is perhaps one of the most versatile functions I’ve encountered in my C programming journey. It plucks out switches from the list of command line arguments, processing valid ones and spitting out the trash. It’s really quite amazing, but it’s not without its quirks.
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Globbing is the use of wildcards to match filenames, which is something I touched upon a few Lessons ago. It lead me to the glob() function, which reads a pathname for matching files. Often mentioned along with the glob() function, is the fnmatch() function, which serves a similar purpose.
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Back in May, I wondered how command line input could be processed when a wildcard is present (Lesson link). My research lead me to the glob() function, but you don’t use this function to process a command line wildcard argument. The reason is that these wildcards are handled by the shell; your code has no direct way to determine when a wildcard is present as a command line argument.
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Looks like your stock had a great day at the market. It bounced around, highs and lows, lots of nerves wracked and fingernails chewed, but the price ended higher on the day.
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From the history of the Unix operating system, glob is the term used for wildcard matching in filenames. It’s short for global, which to me means that two extra bytes of storage (for 'a' and 'l') were important back in the day.
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Stock prices fluctuate throughout the day based on news, fear, and speculation. If you own stock and desire the price to rise, you anxiously watch the stock tickers throughout the day, puzzled or delighted by the reactions. This month’s Exercise attempts to emulate such anxiety.
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Wildcards were highly useful during the glory days of text mode operating systems. They still exist: ? represents a single character in a filename and * represents a group of characters. Using wildcards to manipulate files is a staple of computer file management, perhaps a lost art in the era of graphical operating systems, but still relevant. The C language is also still relevant, so how does it deal with wildcards in a filename?
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Unlike the iffy issue with assigning a pointer directly to a string, you cannot declare a pointer and assign it an immediate value. This puzzle was presented in last week’s Lesson. No, to do things properly requires not a single statement but three separate steps.
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