How can I use a file in a command and redirect output to the same file without truncating it?

Question

Basically I want to take as input text from a file, remove a line from that file, and send the output back to the same file. Something along these lines if that makes it any

Answer 1

There's also ed (as an alternative to sed -i):

# cf. http://wiki.bash-hackers.org/howto/edit-ed
printf '%s\n' H 'g/seg[0-9]\{1,\}\.[0-9]\{1\}/d' wq |  ed -s file_name