There is only one command you need to know, which will help you to identify and categorize all the seven different file types found on the Linux system.

# ls -ld <filename>

ls command will show the file type as an encoded symbol found as the first character of the file permission part. It is important to point out that Linux file types are not to be mistaken with file extensions.
Seven different types of Linux file types and ls command identifiers:

• - : regular file
• d : directory
• c : character device file
• b : block device file
• s : local socket file
• p : named pipe
• l : symbolic link

Regular file
The regular file is a most common file type found on the Linux system. It governs all different files such us text files, images, binary files, shared libraries, etc.

# ls -ld /etc/resolv.conf

-rw-r--r--. 1 root root 54 Jul  3 13:37 /etc/resolv.conf

Directory
Directory is second most common file type found in Linux.

# ls -ld /etc

drwxr-xr-x. 138 root root 8192 Jul  3 13:37 /etc

Character device file
Character and block device files allow users and programs to communicate with hardware peripheral devices.

# ls -ld /dev/zero

crw-rw-rw-. 1 root root 1, 5 Jul  3 13:37 /dev/zero

Block device file
Block devices are similar to character devices. They mostly govern hardware as hard drives, memory, etc.

# ls -ld /dev/vda

brw-rw----. 1 root disk 252, 0 Jul  3 13:37 /dev/vda

Local socket file
Local domain sockets are used for communication between processes. Generally, they are used by services such as X windows, syslog and etc.

# ls -ld /dev/log

srw-rw-rw-. 1 root root 0 Jul  3 13:37 /dev/log

Named pipe
Similarly as Local sockets, named pipes allow communication between two local processes. A named pipe can be used to transfer information from one application to another without the use of an intermediate temporary file.

Symbolic link
With symbolic links an administrator can assign a file or directory multiple identities. Symbolic link can be though of as a pointer to an original file. There are two types of symbolic links:

• hard links
• soft links

The difference between hard and soft links is that soft links use file name as reference and hard links use direct reference to the original file. Furthermore, hard links cannot cross file systems and partitions.

# ls -ld /dev/rtc

lrwxrwxrwx. 1 root root 4 Jul  3 13:37 /dev/rtc -> rtc0

CentOS 7

No features.

openSUSE Leap 42.3

No features.

Ubuntu 17.04

No features.