I'm learning what the entries in /dev represent and how programs use them. I understand that they aren't ordinary files stored on the disk, but I'm not clear on why they exist or how software interfaces with them. For example, are there libraries or command-line utilities that read from or write to /dev/random, /dev/urandom, /dev/zero, and /dev/null?
3 Answers
Yes—many programs and scripts use these device files directly through normal file operations. Entries in /dev are special interfaces provided by the operating system, allowing hardware and kernel services to be accessed using familiar operations such as opening, reading, and writing files. For example, a program can read from /dev/random or /dev/urandom when it needs random bytes, while shell commands can redirect output to /dev/null when they want to discard it.
The “everything is a file” idea is a convenient Unix interface, not a claim that every entry is a normal disk file. The kernel creates these special files so applications can communicate with devices or kernel-provided data streams through standard file APIs. Some entries represent physical devices, while others, such as /dev/random and /dev/null, provide virtual services.
A few common examples are /dev/urandom for generating random data, /dev/zero for producing an endless stream of zero bytes, and /dev/null for accepting and discarding anything written to it. Utilities such as dd can read from or write to these interfaces—for instance, /dev/zero is often used to create a file of a known size. Be careful with commands that write to whole disks, since a typo can destroy data immediately.
Related Questions
Can't Load PhpMyadmin On After Server Update
Redirect www to non-www in Apache Conf
How To Check If Your SSL Cert Is SHA 1
Windows TrackPad Gestures