How to Append Text to a File Using Bash

1. Append Text to a File With the Redirection Operator >>
2. Append Text to a File With the tee Command

We can append text to a file using the Redirection (>>) operator, and the tee command.

We must make sure we have enough permissions to add text to the file. If we do not have enough permissions, we may get permission denied error.

Append Text to a File With the Redirection Operator >>

The redirection operator >> fetches the output from the bash commands and appends the output to another file. There are a lot of ways to print the text to the standard output, however echo and printf are the most popular commands.

To append the text to a file, we write a command to print the text using any of the output commands and then append the >> operator to the command followed by name of the file where the text needs to be added.

echo "Hello World" >> abc.txt

This will add the text Hello World at the end of the file abc.txt.

If the file doesn’t exist in the current working directory, the command will create an empty file and write the text Hello World in the file.

To interpret the escape sequence characters such as \n we use the -e option with the echo command.

echo -e "Hello World! \nThis is DelftStack" >> abc.txt

This will append the text

Hello World!
This is DelftStack

to the file abc.txt.

To verify whether the text has been appended or not, we can use the cat command to view the contents of the file.

cat abc.txt

Output:

Hello World! 
This is DelftStack

If the text has been appended, we can see the text at the end of the file.

If we want more formatted text, we can use the printf command to produce more formatted output.

printf "The path of shell interpreter is %s\n" $SHELL >> abc.txt

It adds the text The path of shell interpreter is /bin/bash to the file abc.txt.

Append Text to a File With the tee Command

tee is a command-line utility that takes input from standard input and writes it to one or more files and standard output simultaneously.

By default, the tee command overwrites the content of the files. To just append the text at the end of the file, we use the -a or --append option with the command.

echo "Hello World!" | tee -a abc.txt

Output:

Hello World!

It appends Hello World! to the file abc.txt and also writes the text to the standard output in the terminal.

If we get permission denied error while appending text to a file, we can add the sudo keyword before the tee command.

echo "Hello World!" | sudo tee -a abc.txt

If we don’t want to see the standard output, we can redirect the output to /dev/null

 echo "Hello World!"  | tee -a abc.txt >/dev/null

One advantage of using the tee command is that we can write the text to multiple files simultaneously using tee command. To write the text to multiple files, we can just list all the files separated by a space.

echo "Hello World!" | sudo tee -a abc.txt backup.txt

It appends the text to both files abc.txt and backup.txt simultaneously.