[prog] using sed on multiple files

[Dan]

> But I need it to permanently make the change not just spit the output 
> to STDOUT

Try using sed's cousin ed, a very primitive file editor. ed takes
keyboard commands similar to those preceded by a ":" in vi, and its
input can be piped.

For example:

ed foo.txt <<EOF
1,\$s/foo/bar/g
wq
EOF

Note: you would normally write 1,$s/foo/bar/g (which means: execute the
substitution on each line from line 1 to the end ($)). However, you need
the backslash to avoid the shell expanding the "$s".

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