Saving command in linux

How to Save Command Output to a File in Linux

There are many things you can do with the output of a command in Linux. You can assign the output of a command to a variable, send it to another command/program for processing through a pipe or redirect it to a file for further analysis.

In this short article, I will show you a simple but useful command-line trick: how to view output of a command on the screen and also write to a file in Linux.

Viewing Output On Screen and also Writing to a File

Assuming you want to get a full summary of available and used disk space of a file system on a Linux system, you can employ the df command; it also helps you determine the file system type on a partition.

Check Filesystem Disk Space

With the -h flag, you can show the file system disk space statistics in a “human readable” format (displays statistics details in bytes, mega bytes and gigabyte).

Disk Space in Human Readable Format

Now to display the above information on the screen and also write it to a file, say for later analysis and/or send to a system administrator via email, run the command below.

Linux Command Output to File

Here, the magic is done by the tee command, it reads from standard input and writes to standard output as well as files.

If a file(s) already exists, you can append it using the -a or —append option like this.

Note: You can also use pydf an alternative “df” command to check disk usage in different colors.

For more information, read through the df and tee man pages.

You may also like to read similar articles.

In this short article, I showed you how to view output of a command on the screen and also write to a file in Linux. If you have any questions or additional ideas to share, do that via the comment section below.

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How to save file in Linux using cat command

Linux cat command syntax

The syntax is:
cat filename
cat file1 file2 file3
cat [options] filename
cat > filename
cat >> filename

Showing file contents

Displaying /etc/hosts file contents in your terminal

Want to redirect contents of file to another?

Execute the following command to copy the contents of input.txt to output.txt using the > operator :
cat input.txt > output.txt
Of course, you can send output of any command to file too:
ls > dirs.txt
cat dirs.
Finally, one can use the >> operator to append the contents of files or command output to files too:
cat foo.txt >> bar.txt
date >> bar.txt
cat bar.txt

How to save file using cat command in Linux

Let us see how to make or create a file using cat command. It is recommended that you use a cat command when you need to create tiny files as it easier using a text editor such as nano or vim.

Step 1 – Create a new file named todays.txt using cat

We are going to create a new file, use the cat command as follows:
cat > todays.txt
Press the ENTER key. Type data you want. For example:
This is a test
Today’s date is Feb/13/2003

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Step 2 – Press the CRTL + D to save the file.

Simply hit the CRTL + D to save the file created by the cat command. To display, enter:
cat todays.txt

Gif 01: Creating and saving small files with cat command

Step 3 – Creating, saving and appending data to files

Please note that if a file named todays.txt is already existed, it will be overwritten by the cat. Use the >> shell operator to append the data/text to an existing file named todays.txt as follows:
cat >> todays.txt

Other cat command examples

Let us see how to print line numbers:
cat -n

/bin/gif
Sample outputs:

To see non printing characters such as $ (end of line), tabs and others, run:
cat

/bin/is_mounted.sh
Sample outputs:

See cat command man page online here or type the following man command:
man cat

Conclusion

We learned how to use the cat command to display or create a new file on Linux.

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How To: Vi / Vim Save And Quit The Editor Command

Tutorial details
Difficulty level	Easy
Root privileges	No
Requirements	vi / vim
Est. reading time	Less than 1 min

vi or vim (Vi IMproved) is text editor or a programmers text editor. You can edit programs or configuration files on the Linux/Unix server. Vim is upwards compatible to Vi. This page explains how to save a file in Vim or vi and quit the editor under Linux or Unix-like systems.

Vim Save And Quit The Editor Command

The procedure to save a file in vim / vi and quit the editor is as follows:

1. Open the terminal application in Linux or Unix
2. Next, open a file in vim / vi, type: vim filename
3. To save a file in Vim / vi, press Esc key, type :w and hit Enter key
4. One can save a file and quit vim / Vi by pressing Esc key, type 😡 and hit Enter key

Let us see all commands and examples in details.

How to open a file in Vim / Vi

You can start vi/vim by typing the following command:
vim file
vi file
vim [options] filename
vim helloworld.sh

Understanding vim modes

When we start vim/vi text editor, we are in normal mode. This mode allows use to use vim commands and navigate around the file as per our needs. In order to edit text, you need to enter the insert mode by pressing i key. This way, we can edit our program or configuration files such as /etc/nginx/nginx.conf.

Of course, you can go back to normal mode by pressing Esc key again.

How to save and quit the vi or vim text editor

To save and quit the vi or vim editor with saving any changes you have made:

1. If you are currently in insert or append mode, press Esc key.
2. Press : (colon). The cursor should reappear at the lower left corner of the screen beside a colon prompt.
3. Enter the following command (type 😡 and press Enter key):

Press ENTER key

This will quit the editor, and all changes you have made to the document will be saved to the file.

Use x to save a file and exit:

Fig.01: Vi / vim save and quit demo.

How to trash all changes in vi/vim

If you do not want to save any changes, first press Esc key. To exit Vim without saving changes press :q! followed by ENTER key.

Getting more help about vim commands

Want to learn vim text editor? Start the vim tutor by typing the following command at the Linux, macOS, and Unix-like system:
$ vimtutor
$ vimtutor it
$ vimtutor fr

vimtutor in action

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Summary of vim/vi commands

Command	Description
Press the ESC key Type :q! Press the ENTER key	Exit vim without saving changes i.e. discards any changes you made.
Press the ESC key Type :wq Press the ENTER key	Save a file and exit.
Press the ESC key Type 😡 Press the ENTER key	Save a file and exit.

Conclusion

You learned how to save a file in vim and exit the text editor using various vim commands. See the vim site or the following pages for more information.

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Category	List of Unix and Linux commands
Documentation	help • mandb • man • pinfo
Disk space analyzers	df • duf • ncdu • pydf
File Management	cat • cp • less • mkdir • more • tree
Firewall	Alpine Awall • CentOS 8 • OpenSUSE • RHEL 8 • Ubuntu 16.04 • Ubuntu 18.04 • Ubuntu 20.04
Linux Desktop Apps	Skype • Spotify • VLC 3
Modern utilities	bat • exa
Network Utilities	NetHogs • dig • host • ip • nmap
OpenVPN	CentOS 7 • CentOS 8 • Debian 10 • Debian 8/9 • Ubuntu 18.04 • Ubuntu 20.04
Package Manager	apk • apt
Processes Management	bg • chroot • cron • disown • fg • glances • gtop • jobs • killall • kill • pidof • pstree • pwdx • time • vtop
Searching	ag • grep • whereis • which
Shell builtins	compgen • echo • printf
Text processing	cut • rev
User Information	groups • id • lastcomm • last • lid/libuser-lid • logname • members • users • whoami • who • w
WireGuard VPN	Alpine • CentOS 8 • Debian 10 • Firewall • Ubuntu 20.04

Comments on this entry are closed.

w!= save without exiting
q!= exit without saving

To save and quit:
If you are currently in insert or append mode, press Esc key.
Press: (semi-colon) The cursor should reappear at the lower left corner of the screen beside a colon prompt.
Enter the following command (type wq! and press Enter key).
🙂

Press: (colon) The cursor should reappear at the lower left corner of the screen beside a colon prompt.
colon is right.

none of these commands are working

Hit the ‘esc’ key and it will take you out of the cursor mode and give you a cursor at the lower left hand of the screen. Now enter wq! and it will save and quit.

Worked for me (Ubuntu 16.4). Thanks

Thanks for sharing knowledge!
Worked just perfectly!

worked for me too on Ubuntu. thank you!

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How to Save the Output of a Command to a File in Linux Terminal [Beginner’s Tip]

Last updated April 17, 2021 By Abhishek Prakash 3 Comments

When you run a command or script in the Linux terminal, it prints the output on the screen for your immediate viewing.

There will be times when you need to save the output to a file for future references. Now, you can surely copy and paste in Linux terminal but there are better ways to save the output of a shell script or command in Linux command line. Let me show them to you.

Method 1: Use redirection to save command output to file in Linux

You can use redirection in Linux for this purpose. With redirection operator, instead of showing the output on the screen, it goes to the provided file.

• The > redirects the command output to a file replacing any existing content on the file.
• The >> redirects adds the command output at the end of the existing content (if any) of the file.

Use the STDOUT redirection operator > for redirecting the output to a file like this:

If the file.txt doesn’t exist, it will be created automatically. If you use the > redirect again with the same file, the file content is replaced by the new output.

The example below demonstrates it better. It first saves the output of ls -l command. And then later, it replaces the content of the file with the output of ls *.c command.

If you don’t want to lose the content of the existing file while saving the output of a script or command, use the redirection operation in append mode with >>.

This example demonstrates it better:

Even here if the file doesn’t exist, it is created automatically.

Bonus Tip: Save Linux command output as well as error to a file

If your Linux command returns an error, it doesn’t get saved in the file. You can save both the command output and command error in the same file using 2>&1 like this:

command > file.txt 2>&1

Basically, 0 stands for standard input, 1 for standard output and 2 for standard error. Here, you are redirecting (>) standard error (2) to same address (&) as standard output (1).

Method 2: Use tee command to display the output and save it to a file as well

By the way, did you notice that when you send the command output to a file, you cannot see it anymore on the display? The tee command in Linux solves this problem for you.

Like a tee pipe that sends water stream into two directions, the tee command send the output to the display as well as to a file (or as input to another command). You can use it like this:

Again, the file will be created automatically, if it doesn’t exist already.

You may also use the tee command in append mode with option -a in this manner:

Let me demonstrate it with some easy to follow examples:

I have used simple Linux commands in my examples. But rest assured, you can use these methods to save the output of bash scripts as well.

Note: Avoid pipe pitfall while saving command output to file

You probably are familiar with pipe redirection. You may use it to combine Linux commands but you cannot pipe the output to a file. It will result in error that filename command not found:

This is because pipe redirects the output of one command to input of another command. And in this case, you give it a file name while it was expecting a command.

If you are new to Linux command line, I hope this quick tutorial added to your Linux knowledge a bit. I/O redirection is an essential concept that one should be aware of.

As always, questions and suggestions are always welcome.

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