What's the easiest/quickest way to interleave the lines of two (or more) text files? Example:
File 1:
line1.1
line1.2
line1.3
File 2:
line2.1
line2.2
line2.3
Interleaved:
line1.1
line2.1
line1.2
line2.2
line1.3
line2.3
Sure it's easy to write a little Perl script that opens them both and does the task. But I was wondering if it's possible to get away with fewer code, maybe a one-liner using Unix tools?
@Sujoy's answer points in a useful direction. You can add line numbers, sort, and strip the line numbers:
(cat -n file1 ; cat -n file2 ) | sort -n | cut -f2-
Note (of interest to me) this needs a little more work to get the ordering right if instead of static files you use the output of commands that may run slower or faster than one another. In that case you need to add/sort/remove another tag in addition to the line numbers:
(cat -n <(command1...) | sed 's/^/1\t/' ; cat -n <(command2...) | sed 's/^/2\t/' ; cat -n <(command3) | sed 's/^/3\t/' ) \
| sort -n | cut -f2- | sort -n | cut -f2-
With GNU sed:
sed 'R file2' file1
Output:
line1.1 line2.1 line1.2 line2.2 line1.3 line2.3