When working with Bash, there may be times when you need to add text to a file. Fortunately, there are several ways to accomplish this task. This article explains some of them.
To add text to a file, you must have write permissions on it. Otherwise, you will receive a permission denied error.
Append to a file using the redirection operator (>>)
Redirection allows you to take the output from one command and send it as input to another command or file. The
>> redirection operator appends the output to a given file.
There are a number of commands you can use to print text to standard output and redirect it to the file. The two most commonly used commands for this purpose are
To add text to a file, run the command that prints the text and specifies the file name after the redirection operator:
echo "this is a new line" >> file.txt
When used with the
-e option, the
echo command interprets backslash characters as newlines
echo -e "this is a new line \nthis is another new line" >> file.txt
To produce more complex output, you can use the
printf command, which allows you to specify the formatting of the output:
printf "Hello, I'm %s.\n" $USER >> file.txt
Another way to add text to a file is to use the Here document (Heredoc). It's a type of redirection that allows you to pass multiple lines of input to a command.
For example, you can pass the contents to the
cat command and add it to a file:
cat << EOF >> file.txt
The current working directory is: $PWD
You are logged in as: $(whoami)
You can add the output of any command to a file. Here is an example with the
date +"Year: %Y, Month: %m, Day: %d" >> file.txt
When appending to a file using a redirect, be careful not to use the
> operator to overwrite an existing important file.
Add to a file using the
tee is a Linux command line utility that reads from standard input and writes to both standard output and one or more files simultaneously.
By default, the
tee command overwrites the specified file. To append the output to the file use
tee with the
--append ) option:
echo "this is a new line" | tee -a file.txt
If you don't want
tee write to standard output, redirect it to
echo "this is a new line" | tee -a file.txt >/dev/null
The advantage of using the
tee command over
>> operator is that
tee allows you to simultaneously add text to multiple files and write to files owned by other users in conjunction with
To add text to a file for which you do not have write permissions, prepend it with
tee shown below:
echo "this is a new line" | sudo tee -a file.txt
tee receives the output of the
echo command, elevates sudo permissions, and writes to the file.
To add text to more than one file, specify the files as arguments to the
echo "this is a new line" | tee -a file1.txt file2.txt file3.txt
If you're working with Linux and need to add text to an existing file, you have a couple of options. One way is to use the redirect
>> operator, which will append the text to the end of the file without overwriting any existing content. Another option is to use the
tee command, which not only adds the text to the file, but also displays it on the screen as it is added.
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