awk doesn't use perl or python type regular expressions but much simpler ones, called "extended". Your constructs are managed by Gnu awk with the --posix option only. The following achieves what you want in a simpler way niobe% echo "/"|awk 'gsub(/\/+/,"/")' / niobe% echo "//"|awk 'gsub(/\/+/,"/")' / -- Michel TALON