Adding text to file linux

Linux append text to end of file

You need to use the >> to append text to end of file. It is also useful to redirect and append/add line to end of file on Linux or Unix-like system.

How to redirect the output of the command or data to end of file

The procedure is as follows

1. Append text to end of file using echo command:
   echo ‘text here’ >> filename
2. Append command output to end of file:
   command-name >> filename

How to add lines to end of file in Linux

The >> is called as appending redirected output. Create the file if does not exists. For example, append some networking command to net.eth0.config.sh script:
echo ‘I=eth0’ >> net.eth0.config.sh
echo ‘ip link set $I up’ >> net.eth0.config.sh
echo ‘ip addr add 10.98.222.5/255.255.255.0 dev $I’ >> net.eth0.config.sh
echo ‘ip route add default via 10.98.222.1’ >> net.eth0.config.sh

You can also add data to other config files. Another option is to run command and append output to a file. Run data command at the terminal and append output to output.txt:
date >> output.txt
Execute ls command and append data to files.txt:
ls >> files.txt
To see files.txt use cat command:
cat files.txt
more files.txt
less files.txt

How to append standard output and standard error

The following sytax allows both the standard output (file descriptor 1) and the standard error output (file descriptor 2) to be appended to the file name. The format for appending standard output and standard error is:
echo ‘text’ &>>filename
command &>>filename
find . type d -name «*.projects» &>> list.txt
This is semantically equivalent to
echo ‘text’ >>fileNameHere 2>&1
command >>fileNameHere 2>&1
date >>data.txt 2>&1

For more info read redirection topic.

Append text when using sudo

Try the tee command:
echo ‘text’ | sudo tee -a my_file.txt
echo ‘104.20.186.5 www.cyberciti.biz’ | sudo tee -a /etc/hosts
Of coruse we can use following syntax to append text to end of file in Linux
sudo sh -c ‘echo my_text >> file1’
sudo — bash -c ‘echo «some data» >> /my/path/to/filename.txt’
The -c option passed to the bash/sh to run command using sudo.
See “how to append text to a file when using sudo command on Linux or Unix” for more info.

Conclusion – Append text to end of file on Unix

To append a new line to a text on Unix or Linux, try:

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How to append text to a file when using sudo command on Linux or Unix

Fig.01: How to append/insert text into a file using sudo on Linux or Unix-like system?

Method 1: Use tee command

The tee command read from standard input (such as keyboard) and write to standard output (such as screen) and files. The syntax is:
echo ‘text’ | sudo tee -a /path/to/file
echo ‘192.168.1.254 router’ | sudo tee -a /etc/hosts
Sample outputs:

This solution is simple and you avoided running bash/sh shell with root privileges. Only append or write part needed root permission.

Bash: append to file with sudo and tee

Want to append text to more than one file while using sudo? Try:
echo ‘data’ | sudo tee -a file1 file2 fil3
Verify that you just appended to a file as sudo with cat command:
cat file1
cat file2
We can append to a file with sudo:
cat my_file.txt | sudo tee -a existing_file.txt > /dev/null
It is a good idea to redirect tee output to /dev/null when appending text. In other words, use >/dev/null when you don’t want tee command to write to the standard output such as screen.

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Understanding tee command options

1. -a OR —append : Append to the given FILEs, do not overwrite
2. -i OR —ignore-interrupts : Ignore interrupt signals
3. -p : Diagnose errors writing to non pipes

See tee command man page by typing the following man command man tee

Method 2: Use bash/sh shell

The syntax is:
sudo sh -c ‘echo text >> /path/to/file’
sudo — sh -c «echo ‘text foo bar’ >> /path/to/file»
sudo — bash -c ‘echo data >> /path/to/file’
sudo bash -c ‘echo data text >> /path/to/file’
For example:
sudo sh -c ‘echo «192.168.1.254 router» >> /etc/hosts’
You are running bash/sh shell with root privileges and redirection took place in that shell session. However, quoting complex command can be problem. Hence, tee method recommended to all.

Conclusion

As we learned that there are multiple ways to append text to a file using the sudo command.

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How To Use Cat Command To Append Data To a File on Linux/Unix

I am a new Unix user. I have Debian Linux installed. I need to append text to a file called daily.log. How do I use the cat command to append data to a file?

You can use the cat command to append data or text to a file. The cat command can also append binary data. The main purpose of the cat command is to display data on screen (stdout) or concatenate files under Linux or Unix like operating systems. To append a single line you can use the echo command or printf command command. Let us see how to use the cat command to append data and update files without losing its content.

Tutorial details
Difficulty level	Easy
Root privileges	No
Requirements	cat on Linux or Unix
Est. reading time	2 mintues

How To Use Cat Command To Append Data To a File on Linux/Unix

Redirection symbol is as follows for appending data to a file:

Syntax

Examples

Create a text file called foo.txt, type:

To save the changes press CTRL-d i.e. press and hold CTRL and press d. Create another text file called bar.txt as follows:

Display both files on the screen, enter:

To append a contains of bar.txt to to foo.txt, enter:

To append a ‘Use unix or die’ text to foo.txt file, enter:

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Fig.01: Using the cat and echo command to append a text to a file.

Append text to a file when using sudo command

We can use the echo command or printf command to append data to a file called sales.txt in the current directory:

Want to append to a file? Try:
cat filename | sudo tee -a foo_file.txt
In this example append data using the following syntax:
sudo sh -c ‘echo «192.168.1.253 wireless-router» >> /etc/hosts’
Verify it:
cat /etc/hosts

Summing up

We explained various Linux and Unix commands that one could use to append data to a file. Although I tested all examples on Bash running on macOS and Linux desktop, these examples should work with other shells, too, such as:

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Comments on this entry are closed.

when i execute two commands like echo $val(nn) > t.txt and awk -f throughput.awk wpan.tr >t.txt
i want the file t.txt to have two columns side by side leaving a tab or space in between. but i m getting output like this

pls help in this regard…thanks

I’m not sure I understood your query. To merge corresponding or subsequent lines of files try paste command.

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how to append or add text to a file in linux

Append is defined as “to add something new to something that is existing, as an attachment or supplement“. Sometimes you will need to append text to an already existing text file. This text could come from any source, such as a line of text from the command line, the output of a command or from another text file.

The easiest way to append text is to use the operator ‘>>‘ from the Linux command line. There are two different operators that redirects output to files: ‘>‘ and ‘>>‘, that you need to be aware of.

‘>‘ is used to remove the previous contents before appending the text, while ‘>>‘ appends text while preserving the contents. And also, it always appends the text to the end of the file. So, if you want to append text then you should use the “>>” operator in your commands. We will see some examples of how this is done.

Append Single Line of Text

If you just want to quickly append a small single line of text, then you can use the echo command from the command line.

bash$ echo «This is just a single line of text» >> ./path/filename.txt

Append Text from Command Prompt (Multiple Lines)

If you want to append a long line of text or multiple lines then using the echo command can be cumbersome. In this case, you can direct the stand input (stdin) to the file instead.

When you use the following command, the cat command reads from the stdin and the “>>” operator redirects the standard input to the file, which means you will not return back to the prompt unless you exit (close the stream) using Ctrl-D

bash$ cat >> ./path/filename.txt

> to append text to file» width=558 height=151 data-ezsrcset=»/wp-content/uploads/linux-append-text-cat.png 558w, /wp-content/uploads/linux-append-text-cat-300×81.png 300w, /wp-content/uploads/linux-append-text-cat-258×70.png 258w» sizes=»(max-width: 558px) 100vw, 558px» data-ezsrc=/wp-content/uploads/linux-append-text-cat.png>

Note: use ctrl-d to exit the input mode

Append Text from another File

The text than you want to append can come from another text file. You can use the cat command along with the append operator to append the content.

bash$ cat myfile.txt >> ./path/filename.txt

You can also use the cat and append operators to merge multiple files as well. If you only want to append specific lines from the text file into the output file, then you may use the grep command to filter the output of cat and then append the results to file.

For example, the following command will append all lines that contain the word chocolate into the file chocolate.txt.

bash$ cat myfile.txt | grep -i «chocolate» >> ./path/chocolate.txt

Append Command Output to File

This works pretty much the same way as described with the earlier examples. The only requirement is that the command that you are using actually do output the results to the standard output.

bash$ date >> ./path/filename.txt

The above command appends the output of date command to the file name filename.txt. You can use any other command as well, such as time, ls, find or grep.

Using sed

Using the “>>” (append) operator is the easiest way to append text to a file from the command line. The other option that you have is the use of sed command.

The following example will append the line “Why redirection? I can use sed.” into the file filename.txt.

bash$ sed -i «$ a\Why redirection? I can use sed.» ./path/filename.txt

The one advantage of sed is that you actually use it to prepend text, as opposed the append. Prepend will add the new text to to the start of the file, while append adds it to the bottom or end of the file.

To prepend text to a file you can use the option 1i, as shown in the example below.

bash$ sed -i ‘1i This is the start of the file’ ./path/filename.txt

The sed command is a really powerful tool when it comes to the text manipulation. It is worthwhile reading through the documentation to find all its features.

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