File Types and Thier Uses

File types in Linux Explained

“How many types of files are there in Linux/Unix and what are they?” This is a common question to every person who starts learning Linux.

Why is it important to know file types?
Ans : This is because Linux will consider every thing as file. So when ever you start working on Linux/Unix box you have to deal with different file types to effectively manage them.

How many types of file are there?
By default Unix have only 3 types of files..
They are.

1. Regular files
2. Directory files
3. Special files(This category is having 5 sub types in it.)

So in practical we have total 7 types of files are there. And in Solaris we have 8 types.

Here are those files type. And you can see the file type indication at leftmost part of “ls -l” command

1. Regular file(-) 

2. Directory files(d) 

Special files 

3. Block file(b) 

4. Character device file(c) 

5. Named pipe file or just a pipe file(p) 

6. Symbolic link file(l) 

7. Socket file(s)

For your information there is one more file type called door files(D) which is present in Sun Solaris as mention earlier. A door is a special file for inter-process communication between a client and server(so total 8 types in Unix machines.).

We will learn about different types of files as below sequence for every file type.
1)Defination and information of the file type
2)How to create particular file type
3)How to list/see particular file type

Regular file type Explained in Linux

These are the files which are indicated with “-” in ls -l output at the starting of the line. And these files are.

1. Readable files or
2. A binary files or
3. Image files or
4. Compressed files etc.

How to create them?

Ans : Use touch/vi command and redirection operators etc.

How can we list them in my present working directory?
ls -l | grep ^-
Example listing of regular files :

-rw-r–r– 1 krishna krishna 20986522 2010-01-31 13:48 test.wmv
-rw-r–r– 1 krishna krishna 173448 2010-01-30 21:20 Transformers-Teaser-Wallpaper-310.jpg
-r-xr-xr-x 1 root root 135168 2009-12-12 19:14 VIDEO_TS.VOB
-rw-r–r– 1 krishna krishna 2113536 2009-12-01 13:32 Aditya 365 – Janavule.mp3
-rwxrwxrwx 1 root root 168 2010-02-14 14:12 xyz.sh

Directory file type explained in Linux/Unix

These type of files contains regular files/folders/special files stored on a physical device. And this type of files will be in blue in color with link greater then or equal 2.

How can we list them in my present working directory?

ls -l | grep ^d

Example listing of directories.
drwxr-xr-x 2 surendra surendra 4096 2010-01-19 18:37 bin
drwxr-xr-x 5 surendra surendra 4096 2010-02-15 18:46 Desktop
drwxr-xr-x 2 surendra surendra 4096 2010-01-18 14:36 Documents
drwxr-xr-x 2 surendra surendra 4096 2010-02-13 17:45 Downloads

How to create them?
Ans : Use mkdir command

Block file type explained

These files are hardware files most of them are present in /dev

How to create them?
Ans : Use fdisk command or create virtual partition.

How can we list them in my present working directory?
ls -l | grep ^b
Example listing of Block files(for you to see these file, they are located in /dev).

brw-rw—- 1 root disk 8, 1 2010-02-15 09:35 sda1
brw-rw—- 1 root disk 8, 2 2010-02-15 09:35 sda2
brw-rw—- 1 root disk 8, 5 2010-02-15 09:35 sda5

Character device files

Provides a serial stream of input or output.Your terminals are clasic example for this type of files.
How can we list chracter files in my present working directory?
ls -l | grep ^c

Example listing of character files(located in /dev)
crw-rw-rw- 1 root tty 5, 0 2010-02-15 16:52 tty
crw–w—- 1 root root 4, 0 2010-02-15 09:35 tty0
crw——- 1 root root 4, 1 2010-02-15 09:35 tty1

Pipe files explaned

The other name of pipe is a “named” pipe, which is sometimes called a FIFO. FIFO stands for “First In, First Out” and refers to the property that the order of bytes going in is the same coming out. The “name” of a named pipe is actually a file name within the file system.

How to create them?

Ans : Use mkfifo command.

How can we list chracter files in my present working directory?
ls -l | grep ^p

Example listing of pipe files
prw-r—– 1 root root 0 2010-02-15 09:35 /dev/.initramfs/usplash_outfifo
prw-r—– 1 root root 0 2010-02-15 09:35 /dev/.initramfs/usplash_fifo
prw——- 1 syslog syslog 0 2010-02-15 15:38 /var/run/rsyslog/kmsg

Sybolic link files

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 links ie soft and hard link.

How to create them?
Ans : use ln command

How can we list linked files in my present working directory?
ls -l | grep ^l

Example listing of linked files
lrwxrwxrwx 1 root root 24 2010-02-15 09:35 sndstat -> /proc/asound/oss/sndstat
lrwxrwxrwx 1 root root 15 2010-02-15 09:35 stderr -> /proc/self/fd/2
lrwxrwxrwx 1 root root 15 2010-02-15 09:35 stdin -> /proc/self/fd/0
lrwxrwxrwx 1 root root 15 2010-02-15 09:35 stdout -> /proc/self/fd/1

Socket files in Linux

A socket file is used to pass information between applications for communication purpose

How to create them?
Ans : You can create a socket file using socket() system call avialable under

Example
int sockfd = socket(AF_INET, SOCK_STREAM, 0);
You can refer to this socket file using the sockfd. This is same as the file descriptor, and you can use read(), write() system calls to read and write from the socket.

How can we list chracter files in my present working directory?
ls -l | grep ^s

Example listing of socket files.
srw-rw-rw- 1 root root 0 2010-02-15 09:35 /dev/log
srwxrwxrwx 1 root root 0 2010-02-15 10:07 /var/run/cups/cups.sock
srwxrwxrwx 1 root root 0 2010-02-15 09:35 /var/run/samba/winbindd_privileged/pipe
srwxrwxrwx 1 mysql mysql 0 2010-02-15 09:35 /var/run/mysqld/mysqld.sock

A tip for you guys.
How to find your desired type of a file ?

Ans : Use find command with -type option.

For example if you want to find socket file, just use below command.

find / -type s

If you want to find linked file then how?

Find / -type l

Thats it.. You got it..  Enjoy reading..