[SOLVED] Find a line with a single word and merge it with the next line

Issue

I have an issue with grep that i can't sort out.

What I have. A listing of firstnames and lastnames, like:

John Doe
Alice Smith
Bob Smith

My problem. Sometimes, firstname and lastname are disjointed, like:

Alice
Smith
Bob Doolittle
Mark
Von Doe //sometimes, there are more than one word on the next line

What I'd like to achieve. Concatenate the "orphan" name with the next line.

Alice Smith
Bod Doolittle
Mark Von Doe

What I already tried

grep -ozP "^\w+\n\w.+" file | tr '\n' ' '

So, here I ask grep to find a line with just one word and concatenate it with the following line, even is this next line has more than one word.

It works correctly but only if the isolated word is at the very beginning of the file. If it appears below the first line, grep do not spot it. So a quick and dirty solution where I would loop through the file and remove a line after each pass doesn't work for me.

Solution

If awk is acceptable:

awk '
NF==1 {printf "%s ",$1; getline; print; next}
1' names.dat

Where:

• NF==1 - if only one name/field in the current record ...
• printf / getline / print / next - print field #1, read next line and print it, then skip to next line
• 1 - print all other lines as is

As a one-liner:

awk 'NF==1{printf "%s ",$1;getline;print;next}1' names.dat

This generates:

Alice Smith
Bob Doolittle
Mark Von Doe //sometimes, there are more than one word on the next line

Answered By - markp-fuso

Answer Checked By - Pedro (WPSolving Volunteer)