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Description of problem: On RH 9 with sed 4.0.5 : echo "a b" | sed '{:bcl;N;s/\n/ /;t bcl}' gives : a b On FC 1 with sed 4.0.8 echo "a b" | sed '{:bcl;N;s/\n/ /;t bcl}' gives nothing So what ? Version-Release number of selected component (if applicable): sed-4.0.8-2 How reproducible: Always Steps to Reproduce: 1.Cf description 2. 3. Additional info:
My understanding of http://www.opengroup.org/onlinepubs/007904975/utilities/sed.html is that the latter behaviour is correct. "If no next line of input is available, the N command verb shall branch to the end of the script and quit without starting a new cycle or copying the pattern space to standard output."
From /usr/share/doc/sed-4.0.8/BUGS : * NON-BUGS ... `N' command on the last line Most versions of sed exit without printing anything when the `N' command is issued on the last line of a file. GNU sed instead prints pattern space before exiting unless of course the `-n' command switch has been specified. More information on the reason behind this choice can be found in the Info manual.
Paolo Bonzini (sed maintainer) provided a patch which restores the old N behaviour unless POSIXLY_CORRECT is set in the environment. The patch is included in sed-4.0.8-3 in rawhide.