Linux man (manual) Command

Despite the ‘man’ commands, relative simplicity and appearance of unimportance, the ‘man’ command is, perhaps, one of the most important commands to lean in Linux. 

Why the ‘man’ command important?

The true value of the ‘man’ command is that provides access to the online manuals (documentation), which will be consulted often until Linux commands and functions have to be learned and internalized.  Even after learning the more familiar and commonly used Linux command and functions, one will still need to refer the less commonly used capabilities or to confirm something which has been used in a while.

When some the more arrogant Linux users will sometime tell folks with questions to “read the frickin’ manual” (RTFM), the ‘man’ command is what they are usually talking about.  Although there are other perfectly useful reference materials online (e.g., git documentation project) or commercial books, the ‘man’ command should be the go-to place for documentation.  The reason this is actually very simple, if the command or function is installed in your version or environment instance of Linux, then man pages will be available.  Therefore, usually, there will no need to go search on the internet for answers or carrying books around.

The ‘man’ command syntax

The syntax of the ‘man’ command is simple and easy to learn to use.  In fact, the ‘man’ command is so easy to use that people frequently will not even use options when they use the man command and enter ‘man’ command and the keyword.

‘man’ command syntax

man [options] (keywords)

Simple examples to illustrate how to use the ‘man’ command.

Example to pull up the ‘Man’ command documentation

[blog-server ~]$ man man

In this example, the man command is using ‘man man’ to pull up its own online documentation.

Example to pull up the ‘ls’ command documentation

[blog-server ~]$ man ls

In this example, the man command is using ‘man ls’ to pull up the ‘list directory contents‘ online documentation.

list directory contents

Example to pull up the ‘cp’ command documentation

[blog-server ~]$ man cp

In this example, the man command is using ‘man cp’ to pull up the ‘copy files and directories ‘ online documentation.

Example screenshot of the ‘cp’ (copy files and directories) file command online documentation

How to install locate command in Linux Redhat and Centos

To install the locate command (mlocate) in Redhat or Centos, use the ’YUM’ command, install function. 

  • Logon as ‘root’ or use with ‘sudo’ permissions
  • Then, run a ’man’ command to confirm that the locate command is not already installed: ‘man locate’

Example ‘man’ command (as root user)

[root@blog-server ~]# man locate

  • If the ’man’ documentation page returns, then it is already installed.  If no ’man’ documentation page is returned, then run the ‘yum install’ command.
  • Run the ‘yum install’ command as ‘root’ or ‘sudo’ user:

Example ‘yum install’ command (as root user)

[root@blog-server ~]# yum install mlocate

Example ‘yum install’ command (as sudo user)

[root@blog-server ~]# sudo yum install mlocate

Then run the [root@data-server ~]# updated

Example Run ‘updatedb’ Command (as Root user)

[root@blog-server ~]# updated

Example Run ‘updatedb’ Command (as sudo user)

[root@blog-server ~]# sudo updatedb

How To quit the Linux vi editor without saving changes

To quit the Linux ’vi’ editor without saving any changes which have been made:

To Exit the insert or append mode

  1. From within insert or append mode, press the ‘Esc‘ key.

To Enable VI Command Line

  1. Press the ‘:’ (colon) Key. The cursor should reappear in the lower-left corner of the screen beside a colon prompt.
  2. Then, Enter the ‘q!’ Command and press the ‘Enter’ Key.

Example VI Command Line

: q!

This will quit the Linux VI editor, and all changes the document made in this session will be lost.

Linux Move (mv) Command

The Linux move command (mv) is one of the essential commands, which can be very useful in Linux, Unix, and AIX.  The primary purpose of the move command is obviously to move files, and of course, directories.   The move command may also be used to rename files and to make backups.

Move Command Syntax

$ mv [options] source (file or directory)  destination

Move Command options

option description
mv -f force move by overwriting destination file without prompt
mv -i interactive prompt before overwriting
mv -u update – move when the source is newer than the destination
mv -v verbose – print source and destination files
MV – t explicitly saying to move the file or directory here, rather trying to fit everything into the last argument.
mv * Move all (Multiple) files to a specific director without listing by name

For More move command details see the Linux documentation manuals using the man command

$ man mv

mv command examples

Here are some quick and very simple move command (MV) examples for reference.

Move Move to files  to the /Archive/ directory:

$ mv happy.txt garden.txt /Archive/

Move all “.txt” files in the current directory to subdirectory backup:

$ mv *.txt backup

Move all files in subdirectory ‘backup’ to current directory:

$ mv backup/*

Rename file happy.txt to happy.bak filename:

$ mv happy.txt happy.bak

Rename directory backup to backup2:

$ mv backup backup2

Update – move when happy.txt is newer or missing in target directory:

$ mv -u happy.txt backup

Move happy.txt and prompt before overwrite backup / happy.txt:

$ mv -v happy.txt backup

Useful Links – Linux

Here are a few useful references for Linux, which may be helpful.

Linux Documentation

Bash Documentation

Links for Major Linux Distributions

CentOS

Red Hat Enterprise Linux (RHEL)

Ubuntu

8 Most Useful Linux Commands For Beginners

Do you think that the command lines are an old-fashion leftover from previous decades or an antiquated way of using a PC? Think again. Indeed, it is one of the most powerful and flexible ways to perform and manage in Linux. If you come from the comfort of a Mac or Window desktop, however, it can be a bit intimidating to get used to Linux commands. Everything is secretive, dark, and anything but friendly to beginners. That’s why we have rounded up this short list of the most useful Linux commands with examples. Keep reading and speed up your learning journey with Linux.

1. Ls command – list files

Ls is one of the most basic and common commands in Linux. You can use it to print contents in the current working directory and see the list of files, directories, or folders on your Linux system.
For instance, the command “ls tourism” will display the users every folder store inside the overall “tourism” folder. Keep in mind that directories and files will be denoted in different colors, which can be selected in the system.
You would also use the command “ls – R” to display all files both in the directories and subdirectories. Since Linux commands are case sensitive, make sure to enter “R” instead of “r” to avoid an error.

2. Cat command – create and view files

You can use the “cat” command to show text files. Also, it would be used for creating, combining, and copying text files. For example, use “cat linux_tip” to get inside the linux_tip file and read its contents on the screen.
To combine two text files “linux_tip_1” and “linux_tip_2, you can enter the following command “cat linux_tip_1 linux_tip_2 > linux_tip”. Keep in mind that only text documents would be combined and shown with this command.

3. Rm command – delete files

The “Rm” command can be used for removing files or directories from your Linux system without confirmation. The syntax is simple “Rm name_deleted_file.”
For example, the command “rm computer_science” will immediately remove the file or directory named “computer_science” from your computer. Make sure to consider carefully before using this command because you cannot get it back.

4. mv command – move and rename files

To move and rename files, the “mv” command will be used. Here is the basic syntax for this task: “mv filename new_location.”
Suppose that you need to move the file name “english_class” to location “/home/school/documents”, just enter the command “mv english_class /home/school/documents.” Keep in mind that this command requires the permission of users.
The syntax for renaming a file is “mv filename newname”. An example command is “mv english_class french_class”

5. Mkdir – create directories

If you want to create a new directory in your Linux system, then you can use the “mkdir” command. The syntax is “mkdir new_directory.”
For instance, you can create a new directory named “final homework” by typing the following command “mkdir final_homework.” In case you do not want to make a parent directory manually, add the -p argument. Keep in mind that it is -p, not -P. Everything in Linux is case sensitive.

6. Rmdir command – remove directories

In contrast with the mkdir command, you can use the rmdir command to remove a directory. The syntax is similar: “rmdir removed_directory.”
If you enter the following command “rmdir basketball_data”, it will immediately delete the directory named “basketball_data”. Always check carefully to make sure that there is no sub-directory or file under the deleted directory. If possible, it is always better to delete the sub-directory or files first before moving to the parent one.

7. Man command – seek help in Linux

“Man” simply stands for manual. You can use this command to access a reference book of the Linux system, which is quite similar to the “Help” file in many popular applications or software. To seek help on any commands that you don’t understand, just enter “ma command_name”. The terminal will open a manual page for the typed command.
For example, if you enter “man ls”, the terminal will provide you with basic information on the “ls” command.

8. History command – view previous commands

As you can guess from the name, the “history” command can be used to display all of the commands that you just used previously for the current session. This can be helpful in referring to the old commands and re-entering or re-using them in the next operations.

Related References

Linux – What is yum?

Linux
Linux

In simple terms, yum is a, command-line interface, package manager utility for computers running the Linux operating system, which augments the RPM Package Manager capabilities. yum is the primary tool for getting, installing, deleting, querying, and managing RPM software packages. Also, yum is used in Red Hat Enterprise Linux (RHEL) versions 5 and later.