Shell script to remove new line after numeric string

Question

I need to write a SHELL Script to remove new line after only after a numeric string? or after string doesn\'t start with number. For example a have a file:

asasa         


        

Answer 1

Here you go!

[jaypal~]$ cat file9
asasas
12345
adab-123
123

[jaypal~]$ sed '{N;s/\n/ /g}' file9
asasas 12345
adab-123 123
[jaypal~]$