====== SED - Numbering - Number each line of a file (but only print numbers if line is not blank) ======

<code bash>
sed '/./=' filename | sed '/./N; s/\n/ /'
</code>

----

===== Example =====

Running that command again this file:

<file bash testfile>
aaa
bbb
ccc
</file>

returns:

<file bash testfile>
1 aaa
2 bbb
3 ccc
</file>