Regular expression to match lines in a file that do not start with # or a blank space

threeonethree · 12-25-2010, 01:41 AM

i have a file like this

# comments
#comments
#comments
bla bla
# comments
#bal bla
bla bla
blank space
blank space
bla bla
end of file

i want to grep lines which do not start with # or a blank space. like

bla bla
bla bla

how do i do this?

i tried grep --invert-match '^#' which gives lines not starting with # but gives me blank lines too

i tried grep --invert-match '^#|^ ' which will give lines not starting with # OR not starting with blank ( which means any line including ones starting with #

what is the correct answer? thanks

catkin · 12-25-2010, 01:51 AM

grep -E -v '(^#)|(^ )' file.txt

grail · 12-25-2010, 02:14 AM

I wasn't sure if 'blank space' meant a line with at least a single space on it or an empty line, so for the second option you could use:

Code:

egrep -v '^(#|$)' file

If you want the spaces option too you can add:

Code:

egrep -v '^(#| |$)' file

catkin · 12-25-2010, 03:00 AM

Hi grail

Nice refinement, putting the ^ before the list of expressions.