How to Understand and Identify File Types in Linux

Preface

As we all know, everything in Linux is a file, including hard disks and graphics cards. When navigating in Linux, most of the files you encounter are regular files and directory files. But there are other types, corresponding to 5 different types of effects. Therefore, understanding file types in Linux is very important in many ways.

If you don’t believe it, just read the full article and you will see how important it is. If you don't understand file types, you can't make arbitrary changes without fear.

If you make some wrong changes, you may corrupt your file system, so please be careful when you do this. Files are very important in Linux systems because all devices and daemons are stored as files.

How many types are available in Linux?

As far as I know, there are a total of 7 types of files in Linux, divided into 3 major categories. The details are as follows.

• Ordinary documents

• Catalog File

• Special files (there are 5 file types in this category)

• Linked files

• Character device files
•Socket File
Named pipe files
• Block files

Refer to the following table to better understand file types in Linux.

symbol	significance
–	Normal file. Long lists begin with an underscore _.
d	Catalog file. The long list begins with the letter d.
l	Link files. The long list begins with the letter l.
c	Character device file. The long list begins with the English letter c.
s	Socket file. The long list begins with the English letter s.
p	Named pipe file. The long list begins with the English letter p.
b	Block files. The long list begins with the English letter b.

Method 1: Manually identify file types in Linux

If you know Linux well, then you can easily identify the file types with the help of the above table.

How to view normal files in Linux?

Use the following command to view normal files in Linux. Ordinary files can appear anywhere in the Linux file system. The color of normal files is "white".

# ls -la | grep ^-
-rw------. 1 mageshm mageshm 1394 Jan 18 15:59 .bash_history
-rw-r--r--. 1 mageshm mageshm 18 May 11 2012 .bash_logout
-rw-r--r--. 1 mageshm mageshm 176 May 11 2012 .bash_profile
-rw-r--r--. 1 mageshm mageshm 124 May 11 2012 .bashrc
-rw-r--r--. 1 root root 26 Dec 27 17:55 liks
-rw-r--r--. 1 root root 104857600 Jan 31 2006 test100.dat
-rw-r--r--. 1 root root 104874307 Dec 30 2012 test100.zip
-rw-r--r--. 1 root root 11536384 Dec 30 2012 test10.zip
-rw-r--r--. 1 root root 61 Dec 27 19:05 test2-bzip2.txt
-rw-r--r--. 1 root root 61 Dec 31 14:24 test3-bzip2.txt
-rw-r--r--. 1 root root 60 Dec 27 19:01 test-bzip2.txt

How to view directory files in Linux?

Use the following command to view directory files in Linux. Directory files can appear anywhere in the Linux file system. The color of the catalog file is "blue".

# ls -la | grep ^d
drwxr-xr-x. 3 mageshm mageshm 4096 Dec 31 14:24 links/
drwxrwxr-x. 2 mageshm mageshm 4096 Nov 16 15:44 perl5/
drwxr-xr-x. 2 mageshm mageshm 4096 Nov 16 15:37 public_ftp/
drwxr-xr-x. 3 mageshm mageshm 4096 Nov 16 15:37 public_html/

How to view linked files in Linux?

Use the following command to view the link file in Linux. Link files can appear anywhere in the Linux file system. There are two types of link files available, soft links and hard links. The color of the linked file is "Light Emerald".

# ls -la | grep ^l
lrwxrwxrwx. 1 root root 31 Dec 7 15:11 s-link-file -> /links/soft-link/test-soft-link
lrwxrwxrwx. 1 root root 38 Dec 7 15:12 s-link-folder -> /links/soft-link/test-soft-link-folder

How to view character device files in Linux?

Use the following command to view character device files in Linux. Character device files appear only in certain locations. It appears in the directory /dev. The color of character device files is "yellow".

# ls -la | grep ^c
# ls -la | grep ^c
crw------. 1 root root 5, 1 Jan 28 14:05 console
crw-rw----. 1 root root 10, 61 Jan 28 14:05 cpu_dma_latency
crw-rw----. 1 root root 10, 62 Jan 28 14:05 crash
crw-rw----. 1 root root 29, 0 Jan 28 14:05 fb0
crw-rw-rw-. 1 root root 1, 7 Jan 28 14:05 full
crw-rw-rw-. 1 root root 10, 229 Jan 28 14:05 fuse

How to view block files in Linux?

Use the following command to view the block files in Linux. Chunk files appear only in specific locations. It appears in the directory /dev. The color of the block file is "yellow".

# ls -la | grep ^b
brw-rw----. 1 root disk 7, 0 Jan 28 14:05 loop0
brw-rw----. 1 root disk 7, 1 Jan 28 14:05 loop1
brw-rw----. 1 root disk 7, 2 Jan 28 14:05 loop2
brw-rw----. 1 root disk 7, 3 Jan 28 14:05 loop3
brw-rw----. 1 root disk 7, 4 Jan 28 14:05 loop4

How to view socket files in Linux?

Use the following command to view the socket file in Linux. Socket files can appear anywhere. The color of the Scoket file is "pink". (LCTT translation note: The original description of the location where socket files and named pipe files can appear here and below is incorrect and has been modified.)

# ls -la| grep ^s
srw-rw-rw- 1root root0 Jan 5 16:36system_bus_socket

How to view named pipe files in Linux?

Use the following command to view the named pipe file in Linux. Named pipe files can appear anywhere. The color of named pipe files is "yellow".

# ls -la | grep ^p
prw-------. 1 root root 0 Jan 28 14:06 replication-notify-fifo|
prw-------. 1 root root 0 Jan 28 14:06 stats-mail|

Method 2: How to use the file command to identify file types in Linux

The file command in Linux allows us to identify different file types. There are three test sets here, in this order: file system tests, magic bytes tests, and language tests for identifying file types.

How to use the file command to view ordinary files in Linux

In your terminal simply type the file command followed by the normal file. The file command will read the contents of the file provided and display the exact type of the file.

That's why we see different results for each regular file. See the different results for normal files below.

# file 2daygeek_access.log
2daygeek_access.log: ASCII text, with very long lines
 
# file powertop.html
powertop.html:HTML document,ASCII text, with very long lines
 
# file 2g-test
2g-test:JSON data
 
# file powertop.txt
powertop.txt:HTML document,UTF-8 Unicode text, with very long lines
 
# file 2g-test-05-01-2019.tar.gz
2g-test-05-01-2019.tar.gz:gzip compressed data, last modified: Sat Jan 5 18:22:20 2019, from Unix, original size 450560

How to use the file command to view directory files in Linux?

In your terminal simply type the file command followed by the directory. See the results below.

# file Pictures/
Pictures/:directory

How to view linked files using file command in Linux?

In your terminal simply type the file command followed by the link file. See the results below.

# file log
log:symbolic link to/run/systemd/journal/dev-log

How to use the file command to view character device files in Linux?

In your terminal simply type the file command followed by the character device file. See the results below.

# file vcsu
vcsu:character special(7/64)

How to view block files using file command in Linux?

In your terminal simply type the file command followed by the block file. See the results below.

# file sda1
sda1:block special(8/1)

How to use the file command to view the socket file in Linux?

In your terminal simply type the file command followed by the Socket file. See the results below.

# file system_bus_socket
system_bus_socket:socket

How to view named pipe files using file command in Linux?

In your terminal simply type the file command followed by the named pipe file. See the results below.

# file pipe-test
pipe-test:fifo(named pipe)

Method-3: How to Identify File Type Using stat Command in Linux?

The stat command allows us to view file types or file system status. This utility provides more information than the file command. It displays a lot of information about a file such as size, block size, IO block size, Inode value, links, file permissions, UID, GID, access/update and modification time of the file and other details.

How to use stat command to view normal files in Linux?

In your terminal simply type the stat command followed by the normal file. See the results below.

# stat 2daygeek_access.log
 File: 2daygeek_access.log
 Size: 14406929 Blocks: 28144 IO Block: 4096 regular file
Device: 10301h/66305d Inode: 1727555 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 1000/ daygeek) Gid: ( 1000/ daygeek)
Access: 2019-01-03 14:05:26.430328867 +0530
Modify: 2019-01-03 14:05:26.460328868 +0530
Change: 2019-01-03 14:05:26.460328868 +0530
 Birth: -

How to use stat command to view directory files in Linux?

In your terminal simply type the stat command followed by the directory file. See the results below.

#stat Pictures/
 File: Pictures/
 Size: 4096 Blocks: 8 IO Block: 4096 directory
Device: 10301h/66305d Inode: 1703982 Links: 3
Access: (0755/drwxr-xr-x) Uid: (1000/daygeek) Gid: (1000/daygeek)
Access: 2018-11-24 03:22:11.090000828 +0530
Modify: 2019-01-05 18:27:01.546958817 +0530
Change: 2019-01-05 18:27:01.546958817 +0530
 Birth: -

How to use stat command to view linked files in Linux?

In your terminal simply type the stat command followed by the link file. See the results below.

# stat /dev/log
 File: /dev/log -> /run/systemd/journal/dev-log
 Size: 28 Blocks: 0 IO Block: 4096 symbolic link
Device: 6h/6d Inode: 278 Links: 1
Access: (0777/lrwxrwxrwx) Uid: (0/root) Gid: (0/root)
Access: 2019-01-05 16:36:31.033333447 +0530
Modify: 2019-01-05 16:36:30.766666768 +0530
Change: 2019-01-05 16:36:30.766666768 +0530
 Birth: -

How to use stat command to view character device files in Linux?

In your terminal simply type the stat command followed by the character device file. See the results below.

# stat /dev/vcsu
 File: /dev/vcsu
 Size: 0 Blocks: 0 IO Block: 4096 character special file
Device: 6h/6d Inode: 16 Links: 1 Device type: 7,40
Access: (0660/crw-rw----) Uid: (0/root) Gid: (5/tty)
Access: 2019-01-05 16:36:31.056666781 +0530
Modify: 2019-01-05 16:36:31.056666781 +0530
Change: 2019-01-05 16:36:31.056666781 +0530
 Birth: -

How to view block files using stat command in Linux?

In your terminal simply type the stat command followed by the block file. See the results below.

# stat /dev/sda1
 File: /dev/sda1
 Size: 0 Blocks: 0 IO Block: 4096 block special file
Device: 6h/6d Inode: 250 Links: 1 Device type: 8,1
Access: (0660/brw-rw----) Uid: (0/root) Gid: (994/disk)
Access: 2019-01-05 16:36:31.596666806 +0530
Modify: 2019-01-05 16:36:31.596666806 +0530
Change: 2019-01-05 16:36:31.596666806 +0530
 Birth: -

How to use stat command to view socket files in Linux?

In your terminal simply type the stat command followed by the Socket file. See the results below.

# stat /var/run/dbus/system_bus_socket 
 File: /var/run/dbus/system_bus_socket
 Size: 0 Blocks: 0 IO Block: 4096 socket
Device: 15h/21d Inode: 576 Links: 1
Access: (0666/srw-rw-rw-) Uid: (0/root) Gid: (0/root)
Access: 2019-01-05 16:36:31.823333482 +0530
Modify: 2019-01-05 16:36:31.810000149 +0530
Change: 2019-01-05 16:36:31.810000149 +0530
 Birth: -

How to use stat command to view named pipe files in Linux?

In your terminal simply type the stat command followed by the named pipe file. See the results below.

# stat pipe-test 
 File: pipe-test
 Size: 0 Blocks: 0 IO Block: 4096 fifo
Device: 10301h/66305d Inode: 1705583 Links: 1
Access: (0644/prw-r--r--) Uid: ( 1000/daygeek) Gid: ( 1000/daygeek)
Access: 2019-01-06 02:00:03.040394731 +0530
Modify: 2019-01-06 02:00:03.040394731 +0530
Change: 2019-01-06 02:00:03.040394731 +0530
 Birth: -

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