7 Extremely Useful Linux Commands for Beginners

ls : What's in This Directory?

The command ls stands for list directory contents. And, cleverly, it will do just that: list a directory's contents! Using it with -F will give a list of the directories contents, and denote items that are other directories with a trailing /.

ls -F

On my server returns:

allthethings.txt  important.doc  Indominus/  Misc/  probs.xls  Red Wings/  Spreadsheets/  Work/

In the above case, allthethings.txt, garbage.file, important.doc, and probs.xls are files, and Indominus, Misc, Red Wings, Spreadsheets, and Work, each with the trailing /, are directories!

There are many other options, or switches, such as -F that can be used with ls for improved results. For example:

ls -lFa

Returns:

dr-xr-x---. 10 root root 4096 Apr 17 12:01 .
 drwxr-xr-x. 19 root root 4096 Apr 14 12:45 ..
 -rw-r--r--  1 root root    0 Apr 17 12:00 allthethings.txt
 -rw-------  1 root root  483 Apr 14 12:45 .bash_history
 -rw-r--r--. 1 root root   18 Dec 28  2013 .bash_logout
 -rw-r--r--. 1 root root  176 Dec 28  2013 .bash_profile
 -rw-r--r--. 1 root root  361 Jan  1 01:24 .bashrc
 drwxr-xr-x  3 root root 4096 Jan  1 01:25 .cache/
 drwxr-xr-x  3 root root 4096 Jan  1 01:25 .config/
 -rw-r--r--. 1 root root  100 Dec 28  2013 .cshrc
 -rw-r--r--  1 root root    0 Apr 17 12:01 garbage.file
 -rw-r--r--  1 root root    0 Apr 17 11:58 important.doc
 drwxr-xr-x  2 root root 4096 Apr 17 11:59 Indominus/
 drwxr-xr-x  2 root root 4096 Apr 17 11:57 Misc/
 -rw-------  1 root root   42 Apr 14 12:44 .my.cnf
 -rw-r--r--  1 root root    0 Apr 17 12:00 probs.xls
 drwxr-xr-x  2 root root 4096 Apr 17 11:57 Red Wings/
 -rw-------  1 root root 1024 Jan  1 01:22 .rnd
 drwxr-xr-x  2 root root 4096 Apr 17 11:56 Spreadsheets/
 drw-------  2 root root 4096 Apr 14 12:42 .ssh/
 -rw-r--r--. 1 root root  129 Dec 28  2013 .tcshrc
 drwxr-xr-x  2 root root 4096 Apr 17 11:57 Work/

In the above case two switches are added: -l and -a. The -l uses the long listing format, and the -a switch lists all the files, including hidden files.

Each column contains an important bit of information:

Column | Information | Example

• 1 | Permissions | drwxr-xr-x
• 2 | # of Hard Links | 2
• 3 | User That Owns File or Directory | root
• 4 | Group for File or Directory | root
• 5 | File Size | 4096
• 6 | Timestamp | Apr 17 11:59
• 7 | Filename | Indominus/

pwd : What Directory Am I Running Commands In?

Before deleting anything, it's always helpful to know what directory you're in; the pwd command will tell you and stands for present working directory:

pwd

Returns the full path name:

/home/dinosaursareawesome

Checking the present working directory can prevent errors when you're using commands that will remove files or directories... in fact, it can save you from a lot of stress and headache!

cd : Move Me to This Other Directory! Stat!

The cd command stands for change directory and is used extremely frequently.

For example, if you're currently in your home directory /home/dinosaursareawesome:

pwd
/home/dinosaursareawesome

But want to change to another directory within that directory... say... Velociraptor:

ls -laF
ls -laF

Then you can use the following command to change to Velociraptor:

cd Velociraptor/

And then verify that you made it to the right directory:

pwd
/home/dinosaursareawesome/Velociraptor

touch : Create This File, or Update the Timestamp on That File!

The touch command is generally used to change file timestamps, but it can also be used for creating a new file.

Let's look at changing a time stamp first. In the case below, I have a file named Foxtrot in the current directory, that was created on Apr 14 12:46:

ls -laF
drwxr-xr-x 2 root root 4096 Apr 17 16:54 ./
drwxr-xr-x 3 root root 4096 Apr 17 16:44 ../
-rw-r--r-- 1 root root 5262 Apr 14 12:46 Foxtrot

Now, let's say I wanted to update that timestamp, Apr 14 12:46 to the current timestamp, but without changing the file. Simply touch the file:

touch Foxtrot

And then check the new timestamp and you'll see it has been updated to the current time, which for me is Apr 17 17:01:

ls -laF
drwxr-xr-x 2 root root 4096 Apr 17 16:54 ./
drwxr-xr-x 3 root root 4096 Apr 17 16:44 ../
-rw-r--r-- 1 root root 5262 Apr 17 17:01 Foxtrot

The second use of the command is to create a file. Let's say I wanted to create the file Golf in my present working directory:

touch Golf

Now look for your new file:

ls -laF
drwxr-xr-x 2 root root 4096 Apr 17 17:04 .
drwxr-xr-x 3 root root 4096 Apr 17 16:44 ..
-rw-r--r-- 1 root root 5262 Apr 17 17:01 Foxtrot
-rw-r--r-- 1 root root    0 Apr 17 17:04 Golf

history : What Have I Done and With Which Commands?

The history command will print a history of all the previously executed commands by the current user. For example:

history
 95  20150417 - 17:01:48 - touch Foxtrot
 96  20150417 - 17:01:50 - ls -laF
 97  20150417 - 17:04:06 - touch Golf
 98  20150417 - 17:04:07 - ls -la

uname : What version am I running?

The uname command is most commonly used to determine which OS you're running, its version, and the kernel version. With the -a switch, it will show: 1. kernel name, 2. network node hostname, 3. kernel release, 4. kernel version, 5. machine hardware name, processor type or "unknown", 6. hardware platform or "unknown", and 7. the operating system.

uname -a
Linux centos7core.thebestfakedomainnameintheworld.com 3.10.0-123.13.2.el7.x86_64 #1 SMP Thu Dec 18 14:09:13 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

• Kernel Name: Linux
• Network Node Hostname: centos7core.thebestfakedomainnameintheworld.com
• Kernel Release: 3.10.0-123.13.2.el7.x86_64
• Kernel Version: #1 SMP Thu Dec 18 14:09:13 UTC 2014
• Machine Hardware Name: x86_64
• Processor Type: x86_64
• Hardware Platform: x86_64
• Operating System: GNU/Linux

man : Help! What Does This Command Do?!

The man command opens manual pages for individual commands; basically, it's your access to quick information on any command. For example, if you wanted to read the manual page for ls, then you would run:

man ls

That's it! Help is that easy to access in Linux!

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