Question

My problem seems to be simple but I found it suprisingly difficult to convert into sed expression.

I need to ‘underscorize’ names between certain tokens in a file. So if the line has tokens : and = I need to convert ‘multi word name’ into ‘multi_word_name’ between these two tokens.

I know it is fairly easy to do two step match anything between the tokens and then global replace spaces with underscores but I can’t find a way of retaining unmatched part of line for writing back into file.

Answer 1

This might work for you (GNU sed, tr and bash):

sed 's/:[^=]*=/$(tr " " "_" <<<"&")/g;s/.*/echo "&"/e' file

or just using sed:

sed ':a;/:[^_=]*=/!b;s//\n&\n/;h;s/.*\n\(.*\)\n.*/\1/;y/ /_/;H;g;s/\n.*\n\(.*\)\n\(.*\)/\2\1/;ta' file