If you’ve been using unix or linux long enough, you’ve probably found yourself wishing for more powerful permissions management. For example, if your web development group has been cooperating with another group on a somewhat sensitive project, you’ve probably wished you could easily set it so that those two groups – and only those two groups – could read and write to certain files. Or, as in my case, wished that you could allow the web server user to read and write to files without having to mess with any group permissions. ACLs are the tool that lets you do that.
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For the minification scripts mentioned here, I had to write a program that would go through every file of a certain type in a directory and process (in this case, minify) that file. At the heart of this problem was the need to get a directory listing.
The obvious way to get a directory listing in C is to use the system call, as in system("ls");. But this is not only lame, it does not work on all systems, and the result cannot be used very easily. The better way to get a directory listing is to use system calls to the filesystem. A complete example is shown at the bottom of this post, as usual.
The functions used in getting a directory listing are opendir and readdir (note: these functions also exist in php, and the code to get a directory listing is in fact nearly the same in php and c). opendir() can be seen as kind of like a fopen() for directories. Following this analogy, readdir() is like a fgetc() for directories. To get a directory listing, we first open the directory with opendir("/dir/name/here"), and then read the name of each file in the directory with a loop of readdir(directory_handle)s. Read the rest of this entry »
