open file and rewrite it with new contents
Haskell
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.gitignore
LICENSE
README
Setup.hs
rewrite.1
rewrite.cabal
rewrite.hs

README

In the Unix shell there is no easy way to use a filter program
to change the contents of a file in-place. For example, if you
want to sort a file in place, this will not work:

sort < myfile > myfile

All that will get you is an empty myfile. This package
gives you the rewrite program, so this will work:

rewrite myfile sort

A --backup option is provided that will copy the existing file
to a backup file before writing the new output. For example,
this will create a file called myfile.bak:

rewrite --backup bak myfile sort

To install, use

cabal install rewrite

There is also a manpage in the source tarball; to install that,
copy it to the right location (typically /usr/local/share/man/man1).