Sending text to standard output is something you learn with your first C program. The common functions are putchar(), puts(), printf(), and so on. When you explore file access, you’ll find familiarity in those functions because they’re quite similar to the standard I/O functions.
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I had such a struggle with file I/O when I first learned computer programming. I knew what a file was and how to create it in an application. With computer programming, however, you enter a lower-level realm that requires more knowledge of file access.
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Your probably familiar with the #include and #define preprocessor directives. You may know a few more, which come in handy for certain coding issues. I have a page on this blog, which goes over some of the common directives, but it doesn’t cover them all. Specifically, it doesn’t cover the preprocessor names.
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The code to recursively plow a directory tree presented in last week’s Lesson could be improved upon. Primarily, it relies upon the .. shortcut to jump back to the parent directory. This method works only some of the time.
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Exploring a folder tree — I mean directory tree — is a procedure found in many file and media utilities. From an original directory, you scan the list of files looking for a subdirectory. When it’s found, you open it and recursively continue the scan.
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O how well I remember DOS. It wasn’t Unix, but it cribbed from Unix heavily. One of the popular DOS commands was DIR, which was like the shell command ls, but more primitive. A typical DOS directory listing looked something like this:
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Not every file listed in a directory is the same. Some entries represent other directories, subdirectories, for example. To determine which entries are mere mortal files and which are directories, you must examine the file type.
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I’m refusing to call it a “folder.” That nonsense gained popularity with the Macintosh and then Windows. Before then, it was a directory, a list of files stored on media. Special C language functions are available to read and manipulate directories, which helps your programs manage files and do other fun file stuff.
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As a beginner, your first exposure to a header file is most likely <stdio.h>, which you understand is necessary for some reason. Then you may confuse the header file with the library, which is common but wrong. And you may even dabble with your own header files. Beyond that, few tutorials bother to mention any necessary details about what should go into a header file and when it’s necessary . . . until now.
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My solution for this month’s Exercise generated a list of duplicated letters in a string. The list also includes blank lines. It’s possible to prevent the blank lines from being displayed, but to do so requires extra programming kung fu.
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