Re: Feature Request - prepend to file

[Bob Proulx]

Eric Blake wrote:
> Brock Noland wrote:
> | I find myself for whatever reason, wanting to prepend a file (or
> | stdin) to a file. Most often when dealing XML that does not have a top
> | level tag.
> |
> | This can be done safely in the shell but requires a lot of work.
> | (Maybe there is already a better way?)
> 
> What shell commands have you been trying?  I find the following to be
> relatively simple to do:
> 
> { echo header; cat file; } > file1 && mv file1 file

In addition to the above if I restrict myself to programs that already
know how to edit files in place I can think of a few additional easy
ways.  Sed of course comes to mind.  Here is one way to use sed to
edit a file in place and insert "foo" at the first line of the file.

sed --in-place '1i\
foo' bar

Using perl:

perl -i -lpe 'print "foo" if $. == 1;' bar

Using ruby:

ruby -i -lpe 'print "foo" if $. == 1' bar

Being an 'ed' fan I would would probably use ed.

ed -s bar <<EOF
i
foo
.
w
q
EOF

Or to read a file "foofile" at the first line of the file.

ed -s bar <<EOF
0r foofile
w
q
EOF

Bob