I received a question from a reader about improperly specifying a printf() placeholder. Specifically, he used %d (decimal integer) to output a string. Most compilers flag this condition as a warning, mismatched types or something similar. Still, the program is created and it runs. What does the output mean?
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The challenge for September’s Exercise is to scramble a string, jumbling its characters in a random pattern. I figured it’s a fun exercise, not anything useless beyond curiosity. Yet such a function exists for the GNU C library, strfry().
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System errors happen. Your program accesses the operating system and . . . something goes wrong. When it does, the function returns -1 and your code must rely upon our old buddy errno to discover what went wrong and possibly output an informative error message.
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There’s a scene in the HBO series Silicon Valley that aptly describes a magic number in programming code: Coders are trying to figure out a compression algorithm and they encounter a large integer value. They wonder what it means; it’s not commented or assigned to a clever constant name. It’s just . . . a magic number.
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In my code, in my books, and in my online courses, I typecast the malloc() function. This is something I’ve done for a while, but never really knew why — until now. I’ve also learned that doing so is considered “bad programming practice” by some in the C community.
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Passing a string to a function? Check!
Passing an array of strings to a function? Watch out!
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You have two choices when modifying a string in a function: You can modify the string directly or you can create a new string and return it. Either way, a new string is created based on the old.
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Despite teaching the C language, I still find myself at odds with pointers. Specifically, it’s the double pointers that remind me of my mortality. I found myself getting into the double pointer polka recently when I tried to work with an array of strings, passing each one individually to a function. O! The pain!
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I enjoy it when an experienced coder reviews my stuff. I’m happy with the feedback, and occasionally they toss me a bone. This time it was a rather obscure bone, but I see the point: Avoid using negative array elements.
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I’ve messed with characters as values quite a few times in my code. Keeping in mind that the char data type is really a tiny integer value, you can perform all kinds of tricks — stuff that drives non-programmers crazy.
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