Restructure csv file Here is an example of the data I'd like to modify: John,, bim,bam,boom tim,tam,toom lam,loom,lim Mary,, pam,pim,poom dam,dim,doom* I try to achieve this: John,bim,bam,boom John,tim,tam,toom John,lam,loom,lim Mary,pam,pim,poom Mary,dam,dim,doom When a name is alone on a line, it becomes a new column in all the rows below til the next name with the same pattern occurs. I wonder if awk or another tool could help but I'm a bit lost. I try to make a condition (if columns 2 and 3 are empty, do something) but that looks a bit complicated for me right now.

You are thinking on the right lines:

> I try to make a condition (if columns 2 and 3 are empty, do something)

Specifically,

* if columns 2 and 3 are empty, save the value of column 1 and continue
* otherwise, prepend the saved value to the line and print it (there are several `awk`ish ways to do this)



So for example


awk -F, '$2=="" && $3=="" {pfx=$1; next} {print pfx "," $0}' file.csv


or more idiomatically using the `FS` field separator variable


awk -F, '$2=="" && $3=="" {pfx=$1; next} {$0 = pfx FS $0; print}' file.csv


or (since the default action - when a rule evaluates true or `1` \- is to print the record)


awk -F, '$2=="" && $3=="" {pfx=$1; next} {$0 = pfx FS $0} 1' file.csv
John,bim,bam,boom
John,tim,tam,toom
John,lam,loom,lim
Mary,pam,pim,poom
Mary,dam,dim,doom