Prevent sed from printing empty stuff

Question

sed -e 's/\([A-Za-z]*\)\( \)\([A-Za-z]*\)\(:\?\)\([A-Za-z]*\)\?\( \)\?\(.*\)\?/[\1][\2][\3][\4][\5][\6][\7]/'

will decorate

class VoxelbuilderAdda:public VoxelBuilder

So it looks like

[class][ ][VoxelbuilderAdda][:][public][ ][VoxelBuilder]

If I instead have

class VoxelBuilder

The output is

[class][ ][VoxelBuilder][][][][]

Is it possible to stop it from printing the empty brackets?

The goal is to print all identifiers with like (square brackets are my simple placeholders but I should have excluded them for the keywords)

\textclassname{VoxelBuilder}

and leave keywords (class, struct, public, ...) and separators like ':' as is.

Obviously an inverted pattern for keywords+separator is more beneficial, but I could not figure it out. I actually want

Replace sequence X with \textclassname{X} only if X is not one of

• class
• struct
• union
• public
• private
• protected
• virtual
• :
• ,
• <
• >

I have stripped out curly braces and semicolon in an earlier step. The goal would be

class \textclassname{VoxelbuilderAdda}:public \textclassname{VoxelBuilder}

With no inheritance

class \textclassname{VoxelbuilderAdda}

If I had the not operator available, It would not only cover those I have, but any weird multiple inheritance as well.

Answer 1

For such kind of conversion is better to use special parse-tools but if you'd like to operate file like a text try:

sed 's/\(::\|[<, ]\)\(\w\+\)/\1\\textclassname{\2}/g' filename

or use -r option to avoid extra-escaping:

sed -r 's/(::|[<, ])(\w+)/\1\\textclassname{\2}/g' filename

Answer 2

so you have to treat spaces, words and colons separately:

sed -e 's/[A-Za-z]\{1,\}/[&]/g' -e 's/:/[&]/g' -e 's/ /[&]/g'

this will replace a) one or more \{1,\} occurences of any letter with the pattern & surrounded by square brackets, b and c) replace a single colon (space) by itself surrounded by square brackets

echo class VoxelbuilderAdda:public VoxelBuilder | sed -e 's/[A-Za-z]\{1,\}/[&]/g' -e 's/:/[&]/g' -e 's/ /[&]/g'
[class][ ][VoxelbuilderAdda][:][public][ ][VoxelBuilder]