Perl for System Administration

Filesystem Differences

We’ll start with a quick review of the native filesystems for each of our target operating systems. Some of this may be old news to you, especially if you have significant experience with a particular operating system. Still, it is worth your while to pay careful attention to the differences between the filesystems (especially the ones you don’t know) if you intend to write Perl code that works on multiple platforms.

Unix

All modern Unix variants ship with a native filesystem with semantics that resemble those of their common ancestor, the Berkeley Fast File System. Different vendors have extended their filesystem implementations in different ways (e.g., Solaris adds Access Control Lists for better security, Digital Unix ships a spiffy transaction-based filesystem called advfs, etc.). We’ll be writing code aimed at the lowest common denominator to allow it to work across different Unix platforms.

The top, or root, of a Unix filesystem is indicated by a forward slash (/). To uniquely identify a file or directory in a Unix filesystem, we construct a path starting with a slash and then add directories, separating them with forward slashes, as we descend deeper into the filesystem. The final component of this path is the desired directory or filename. Directory and filenames in modern Unix variants are case sensitive. Almost all ASCII characters can be used in these names if you are crafty enough, but sticking to alphanumeric characters and some limited punctuation ...