Append

echo "your_line_to_append" >> your_file.txt

history -a

tee --append ~/.ssh/config << END
Host localhost
  ForwardAgent yes
END

Related

• lineinfile

See also

• echo, print, printf, tput, logger, write-output, echo -e, /dev/stdout, banner
• tee, sponge, append, prepend, tee --append