Join lines split with backslash at the end

sed -e '/\\$/{:0;N;s/\\\n//;t0}'
Joins each line that end with backslash (common way to mark line continuation in many languages) with the following one while removing the backslash.
Sample Output
$ sed -e '/\\$/{:0;N;s/\\\n//;t0}' <<END
> Hello \\
> world!
Hello world!
$ echo 'scale=70; 127/131' | bc | sed -e '/\\$/{:0;N;s/\\\n//;t0}'

By: mwgamera
2011-10-09 14:35:23

1 Alternatives + Submit Alt

What Others Think

Very nice. Could you now explain how it works :-)
flatcap · 510 weeks and 3 days ago
PS, your first example is bogus (the second one's good). When you enter text as a 'here document' the shell interprets and leaves a string with an embedded newline (but no backslash). A simple proof is this: cat <<END > Hello \ > World > END Hello World
flatcap · 510 weeks and 3 days ago
Thanks for pointing it out. I fixed the example. It works like this: When a line ending with backslash is read, it reads and appends the following line to the pattern space (the N command) and removes the backslash-newline sequence (s) from the resulting pattern. Finally, before continuing to the next input line, it repeats everything until substitution does not make any changes (t0 conditionally jumps to the :0) so lines spanning over more than two input lines are correctly joined into single output line.
mwgamera · 510 weeks and 3 days ago
Ah, I understand. I bow to you sed mastery!
flatcap · 510 weeks and 2 days ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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