Learn Linux Shell Scripting - Fundamentals of Bash 4.4

File descriptors

You might be tired of hearing it, but it is still no less true: in Linux, everything is a file. We've seen that a file is a file, a directory is a file, even hard disks are files; but now, we'll take this one step further: your keyboard, which you use for input, is also a file!

Complementary to that, your Terminal, which commands use as output, is, guess what: a file.

You can find these files, as with most special files, within your Linux filesystem tree. Let's check our virtual machine:

reader@ubuntu:~$ cd /dev/fd/reader@ubuntu:/dev/fd$ ls -ltotal 0lrwx------ 1 reader reader 64 Nov  5 18:54 0 -> /dev/pts/0lrwx------ 1 reader reader 64 Nov  5 18:54 1 -> /dev/pts/0lrwx------ 1 reader reader 64 Nov  5 18:54 2 -> /dev/pts/0lrwx------ ...