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Old 2nd February 2010
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Carpetsmoker Carpetsmoker is offline
Real Name: Martin
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A quick comment on "1.3 Modifying the '/etc/ttys' file", FreeBSD sed has the -i option, which makes editing files a bit easier:

Code:
     -i extension
	     Edit files in-place similarly to -I, but treat each file indepen-
	     dently from other files.  In particular, line numbers in each
	     file start at 1, the ``$'' address matches the last line of the
	     current file, and address ranges are limited to the current file.
	     (See Sed Addresses.)  The net result is as though each file were
	     edited by a separate sed instance.
And

Code:
     -I extension
	     Edit files in-place, saving backups with the specified extension.
	     If a zero-length extension is given, no backup will be saved.  It
	     is not recommended to give a zero-length extension when in-place
	     editing files, as you risk corruption or partial content in situ-
	     ations where disk space is exhausted, etc.

	     Note that in-place editing with -I still takes place in a single
	     continuous line address space covering all files, although each
	     file preserves its individuality instead of forming one output
	     stream.  The line counter is never reset between files, address
	     ranges can span file boundaries, and the ``$'' address matches
	     only the last line of the last file.  (See Sed Addresses.)  That
	     can lead to unexpected results in many cases of in-place editing,
	     where using -i is desired.
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