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sed substitution or awk, need to direct change the file

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# 8  
Old 08-07-2012
Quote:
Originally Posted by Corona688
Even some implementations of ed may create a temp file.
That temp file is just a scratch file. With ed, the buffer is the source of all writes (allowing for the preservation of inode, hardlinks, softlinks, etc). Unlike gnu sed -i/perl -i which create-rename/rename-create, respectively, with their temp files.


Quote:
Originally Posted by Corona688
It's never a good thing to edit your originals. If you screw up, you've lost data.
That's what backups are for. Further, if you want to be safe, you can trivially create a copy before making any changes. Either with cp or from within ed.

Code:
ed -s "$fname" <<EOED
w $fname.backup
... editing commands here ...
w $fname
q
EOED

If the first write fails for any reason, since stdin is not an interactive device, ed will abort and the edits will not occur.

Regards,
Alister
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