How can I append to a file using dd?

Solution 1:

You can seek to the end of the target file:

sudo echo "# New data" |
    dd of=/etc/config_file conv=notrunc bs=1 seek=$(stat -f "%z" /etc/config_file)

Is there any reason you are using dd rather than output redirection?

The following will work:

echo "# New data" >> /etc/config_file

The >> means add to the end of file if it exists, otherwise create a new file.