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Top Forums Shell Programming and Scripting Delete Blank Lines Between DHCP Host Blocks Post 302258740 by cstovall on Saturday 15th of November 2008 05:24:51 PM
Old 11-15-2008
Both solutions remove the blank lines; however, Joeyg's example removes all blank lines. I just need to match the dhcp host blocks then reove blank lines.

Franklin52's example removes all the blank lines; but, the example first needs to read in the file, copy the output to a new file, then move the new file back to the original.

Any SED gurus have an interactive example? Meaning make the changes take place without piping the output to a new file.

I can copy the host blocks to holding buffer and delete; but, I can not copy them back correctly from the holding buffer. Here is what I got so far:


sed -e '/host/,/}/{h; d;}' -e '/$/{G;}' dhcpd.conf



The above command appends the "}" to the end of the file, not the whole host block. Also, it is not doing it interactively. I tried adding the -i option. It didn't work.
 

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FLIPDIFF(1)							     Man pages							       FLIPDIFF(1)

NAME
flipdiff - exchange the order of two incremental patches SYNOPSIS
flipdiff [[-p n] | [--strip-match=n]] [[-U n] | [--unified=n]] [[-d PAT] | [--drop-context=PAT]] [[-q] | [--quiet]] [[-z] | [--decompress]] [[-b] | [--ignore-space-change]] [[-B] | [--ignore-blank-lines]] [[-i] | [--ignore-case]] [[-w] | [--ignore-all-space]] [--in-place] diff1 diff2 flipdiff {[--help] | [--version]} DESCRIPTION
flipdiff exchanges the order of two patch files that apply one after the other. The patches must be "clean": the context lines must match and there should be no mis-matched offsets. The swapped patches are sent to standard output, with a marker line ("=== 8< === cut here === 8< ===") between them, unless the --in-place option is passed. In that case, the output is written back to the original input files. OPTIONS
-p n, --strip-match=n When comparing filenames, ignore the first n pathname components from both patches. (This is similar to the -p option to GNU patch(1).) -q, --quiet Quieter output. Don't emit rationale lines at the beginning of each patch. -U n, --unified=n Attempt to display n lines of context (requires at least n lines of context in both input files). (This is similar to the -U option to GNU diff(1).) -d pattern, --drop-context=PATTERN Don't display any context on files that match the shell wildcard pattern. This option can be given multiple times. Note that the interpretation of the shell wildcard pattern does not count slash characters or periods as special (in other words, no flags are given to fnmatch). This is so that "*/basename"-type patterns can be given without limiting the number of pathname components. -i, --ignore-case Consider upper- and lower-case to be the same. -w, --ignore-all-space Ignore whitespace changes in patches. -b, --ignore-space-change Ignore changes in the amount of whitespace. -B, --ignore-blank-lines Ignore changes whose lines are all blank. -z, --decompress Decompress files with extensions .gz and .bz2. --in-place Write output to the original input files. --help Display a short usage message. --version Display the version number of flipdiff. LIMITATIONS
This is only been very lightly tested, and may not even work. Using --in-place is not recommended at the moment. There are some cases in which it is not possible to meaningfully flip patches without understanding the semantics of the content. This program only uses complete lines that appear at some stage during the application of the two patches, and never composes a line from parts. Because of this, it is generally a good idea to read through the output to check that it makes sense. AUTHOR
Tim Waugh <twaugh@redhat.com> Package maintainer patchutils 23 January 2009 FLIPDIFF(1)
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