Date: Wed, 7 Oct 2009 17:56:36 -0700 From: George Davidovich <freebsd@optimis.net> To: freebsd-questions@freebsd.org Subject: Re: A general sed question Message-ID: <20091008005636.GA38899@marvin.optimis.net> In-Reply-To: <2daa8b4e0910062345r83fa23aj113b062af114887f@mail.gmail.com> References: <2daa8b4e0910062345r83fa23aj113b062af114887f@mail.gmail.com>
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On Tue, Oct 06, 2009 at 11:45:36PM -0700, David Allen wrote: > I keep bumping up against this, so I thought I'd throw this question out > to those who understand sed better than I do. > > What I'm trying to do is to clean up the contents of some files > (/sys/i386/conf/GENERIC would be a good example) to get more readable > diffs. To that end, I'm trying to use sed to For the following note that what's contained in the square brackets is a space character followed by a literal TAB character (typically created by entering ^V followed by TAB). > - delete commented lines > - remove inline comments s/[ ]*#.*// # takes care of both, but will leave \t\t\t\n > - remove trailing spaces and/or tabs s/[ ]*$// # handy, but not needed if using diff -b > - delete blank lines, and/or lines containing just spaces and/or tabs /^[ ]*$/d > - expand tabs This is overly complex with sed and probably unecessary. Instead I'd suggest using your editor (in vim, it's ':set expandtab | retab'), or for interactive use, relying on expand(1) and using a value for -t that matches the tab spacing you typically use for your pager and/or editor. Alternatively, to get better visual alignment when using diff(1), just use the -t option. Putting the above together, you get sed -e 's/[ ]*#.*//' -e 's/[ ]*$//' -e '/^[ ]*$/d' Hardly ideal but it's readable enough and satisfies the 80/20 rule. If used as a simple alias, shell function or script as Oliver Fromme suggested (yes, this works in bash), my suggestion is diff -ubBt <(cleanup /sys/i386/conf/GENERIC) <(cleanup /path/to/NEWKERNEL) -- George
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