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Everything-is-a-file.md

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In the Linux ecosystem, everything is considered a file, even directories.

The ls command provides the file type

if you run ls -l or ls -al (shows hidden files), the first column in the ouput displays file type and permissions.

  • if the first character is a dash, the file is a regular file
  • if the first character is a b, the file is a block file
  • if the first character is a c, the file is a character file
  • if the first character is a d, the file is a directory
  • if the first character is an l, the file is a symbolic link
  • if the first character is a p, the file is a named pipe
  • if the first character is a s, the file is a socket file

Block files

They provide buffered access to hardware devices.
They communicate with the device drivers through the file system.

Since block files are buffered access type files, they can transfer a large block of data at any given time.

To search for all the block files in your system: ls -l /dev | grep "^b" or ls -l /dev | grep ^b
This command outputs all files in the /dev folder whose name starts with "b". The caret sign ^ means "starts with".

Character files

A character file is also a device file, but it provides unbuffered serial access to your hardware components.
With unbuffered serial access, we can only transfer data one character at a time.

To search for character files: ls -l /dev | grep ^c
This cmd outputs files in the /dev folder whose name starts with a "c".

Symbolic links

They are references to other files on the file system.
To output symbolic links: ls -l /dev | grep ^l

To create a symbolic link: ln -s target link_name
For instance: ln -s .bash_history b_hist

Pipes and named pipes

We use the pipe sign | to pass the output of a command to the input of another command.
A pipe allows inter-process communication (IPC), meaning data transfer between processes running on the same system.
The syntax is: command1 | command2

Pipes can be chained: command1 | command2 | command3

  • A traditional pipe is "unnamed" and lasts only as long as the process.
  • A named pipe, however, can last as long as the system is up, beyond the life of the process.

To create a named pipe: mkfifo pipe1
you can check pipe creation: ls -l | grep ^p

Socket files

Just like pipes, they provide a means of inter-process communication.
Except they transfer the data between processes running on different environments or different machines.

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