Linux file types

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File types

By default Unix have only 3 types of files:

Regular files ('-')
Directory files ('d')
Special files (Actually, this one has 5 types in it.)
1. Block file('b')
2. Character device file('c')
3. Named pipe file or just a pipe file('p')
4. Symbolic link file('l')
5. Socket file('s')

Here are those three types ('-', 'd', and 'l'):

$ ls -l
total 4
drwxrwxr-x 2 k k 4096 Dec  9 09:16 mydir
-rw-rw-r-- 1 k k    0 Dec  9 09:16 myfile1
-rw-rw-r-- 1 k k    0 Dec  9 09:16 myfile2
lrwxrwxrwx 1 k k    7 Dec  9 09:16 my_link -> myfile1

Block file type

These files are hardware files, and most of them are present in /dev. They are created either by fdisk command or by partitioning.

$ ls -l /dev/  | grep ^b
brw-rw----  1 root disk        7,   0 Dec  8 13:31 loop0
brw-rw----  1 root disk        7,   7 Dec  8 13:31 loop7

brw-rw----  1 root disk        1,   0 Dec  8 13:31 ram0
brw-rw----  1 root disk        1,  15 Dec  8 13:31 ram15

brw-rw----  1 root disk        8,   0 Dec  8 13:31 sda
brw-rw----  1 root disk        8,   1 Dec  8 13:31 sda1
brw-rw----  1 root disk        8,   2 Dec  8 13:31 sda2
brw-rw----  1 root disk        8,   3 Dec  8 13:31 sda3

brw-rw----+ 1 root cdrom      11,   0 Dec  8 13:31 sr0

Character device file type

Character device file provides a serial stream of input or output. Our terminals are classic example for this type of files.

$ ls -l /dev/input/mouse0 |grep ^c
crw-r----- 1 root root 13, 32 Dec  9 08:39 /dev/input/mouse0

and:

$ ls -l /dev | grep ^c
crw-------  1 root root        5,   1 Dec  8 13:32 console
crw-------  1 root root       10,  58 Dec  8 13:31 network_throughput
crw-rw-rw-  1 root root        1,   3 Dec  8 13:31 null
crw-r-----  1 root kmem        1,   4 Dec  8 13:31 port
crw-------  1 root root       10, 231 Dec  8 13:31 snapshot
crw-rw-rw-  1 root tty         5,   0 Dec  8 22:41 tty

Pipe file type

$ mkfifo backpipe
$ ls -l
prw-rw-r--   1 k k    0 Dec  9 09:56 backpipe
drwxrwxr-x   2 k k 4096 Dec  9 09:16 mydir
-rw-rw-r--   1 k k    0 Dec  9 09:16 myfile1
-rw-rw-r--   1 k k    0 Dec  9 09:16 myfile2
lrwxrwxrwx   1 k k    7 Dec  9 09:16 my_link -> myfile1

symbolic link file type

These are linked files to other files. They are either Directory/Regular File. The inode number for this file and its parent files are same. There are two types of link files available in Linux/Unix : soft and hard link.

$ ls -l
total 4
drwxrwxr-x 2 k k 4096 Dec  9 09:16 mydir
-rw-rw-r-- 1 k k    0 Dec  9 09:16 myfile1
-rw-rw-r-- 1 k k    0 Dec  9 09:16 myfile2
lrwxrwxrwx 1 k k    7 Dec  9 09:16 my_link -> myfile1

socket file type

A socket file is used to pass information between applications.

$ ls -l /var/run/ | grep ^s
srw-rw-rw- 1 root       root          0 Dec  8 13:31 acpid.socket
srw-rw---- 1 root       docker        0 Dec  8 14:15 docker.sock
srw-rw-rw- 1 root       root          0 Dec  8 13:31 rpcbind.sock
srw-rw-rw- 1 root       root          0 Dec  8 13:31 sdp
srwxr-xr-x 1 root       root          0 Dec  8 13:32 vmnat.5546