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We can use the redirection ( >>) operator and teethe command to append text to a file.

We have to make sure we have enough permissions to add text to the file. If we don't have enough permissions, we may get a permission denied error.

Use the redirection operator >>to append text to a file

The redirection operator takes the output >>from bashthe command and appends it to another file. There are many ways to print text to standard output, but echoand printfare the most commonly used commands.

To append text to a file, we write a command that prints the text using any of the output commands and then append >>the command with the operator followed by the name of the file to which the text needs to be appended.

echo "Hello World" >> abc.txt

This will abc.txtadd the text to the end of the file Hello World.

If the file does not exist in the current working directory, the command will create an empty file and Hello Worldwrite the text to it.

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

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 that the text was added, we can use catthe command to view the contents of the file.

cat abc.txt

Output:

Hello World! 
This is DelftStack

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

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

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

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

Use teethe command to add text to the file

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

By default, teethe command overwrites the contents of the file. If we just want to append the text at the end of the file, we use the -p -aor --append-p option in the command.

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

Output:

Hello World!

It Hello World!appends abc.txtto the file and writes the text to the terminal's standard output.

If we get permission denied error while appending text to the file, we can teeadd sudothe keyword in front of the command.

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

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

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

One benefit of using teethe command is that we can use teethe command to write text to multiple files at the same time. To write text to multiple files, we just need to separate all the files with spaces.

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

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