Classic Shell Scripting

Summary

This completes our tour of the workings of the Unix filesystem. By now, you should be familiar with its main features:

• Files are streams of zero or more 8-bit bytes, without any additional structure other than the use of newline characters to mark line boundaries in text files.

• Bytes are usually interpreted as ASCII characters, but the UTF-8 encoding and the Unicode character set permit graceful evolution of the Unix filesystem, pipes, and network communications to support millions of different characters from all of the world's writing systems, without invalidating the majority of existing files or software.

• Files have attributes, such as timestamps, ownership, and permissions, allowing a much greater degree of access control and privacy than is available on some other desktop operating systems, and eliminating most computer virus problems.

• Access to entire directory trees can be controlled at a single point by suitable settings of directory permissions.

• The maximum file size is large enough to rarely be a problem, and newer filesystem designs raise the maximum well beyond the limits of current technology.

• The maximum filename and pathname lengths are much longer than you are likely to need in practice.

• A clean hierarchical directory structure with slash-separated path components, together with the mount command, allows logical filesystems of potentially unbounded size.

• File-like views of other data are possible, and encouraged, to simplify data processing and use by humans.

• Filenames ...