Using 'grep -e' and more advanced regular expressions

Question

I'm trying to use the following regular expression in grep (searches for mixed case PNG files).

[A-Z]+[\w.]*\.[pPnNgG]{3}[\\"')]*.*$

When I enter the command, my shell displays a > looking for more input.

I can use grep for some basic regular expressions, but I've never quite gotten the handle of using it with more advanced regular expressions.

FWIW, this is in Cygwin on Windows 7.

Answer 1

You did not escape " character. Double backslash before will be replaced with single backslash and " is left not escaped. Either remove one backslash or add one.

Try this regular expression:

grep -i '^[0-9a-z _]\+\.png\([^0-9a-z]+\|$\)' file | grep -v '^[0-9A-Za-z _]\+\.\(png\|PNG\)\([^0-9A-Za-z]\|$\)'

It will match all lines containing from the beginning of the line:

• at least on of characters 0-9 (range of 0, 1, ..., 9 characters), a-z ' ' (space), '_'
• a dot (needs to be escaped with backslash, otherwise it will mean 'any single character')
• 'png' (or 'Png', etc. because -i is added)
• and not followed by any of 0-9 and a-z characters (or A-Z because -i is added).

-i - will disable case sensitivity