Shell Programming and Scripting

I'm pretty experienced with regexps, but I just can't get this expression to work.

The first line of my test file is this:

**** info Fri Jun 04 12:37:58 PDT 2010 stuff

I'm piping this file into this:

egrep '^****\s+[a-z]+[\t ]*Fri Jun 04'

This returns 0 lines.

If I change the expression to "^****\s+[a-z]+[\t ]*", it does find lines, but I need to be able to specify the date string.

I must be missing something simple, but I just don't see it.

Code:

egrep '^\*\*\*\*\s+[a-z]+[\t ]*Fri Jun 04'

maybe? :P

* is a special character in regular expressions, meaning 'zero or more of the previous character'. So the regex "a*" would match an empty string, a, aa, aaaaaaaaaaaaa etc. To match a literal * you need to escape them.

Code:

# This matches other things since * are length specifiers, not literals
$ echo "que" | egrep "^***"
que
# this rejects the string 'que' like it should
$ echo "que" | egrep "^\*\*\*"
# ...and matches *** like it should
$ echo "***" | egrep "^\*\*\*"
***
$

Yeah, missing the "\*" was a stupid mistake. It's still not working, however.

If I use '^\*\*\*\*\s*[a-z]*\s*', it finds lines, but not '^\*\*\*\*\s*[a-z]*\s*Fri Jun'.

If I change it to '^\*\*\*\*\s+[a-z]*\s*' or '^\*\*\*\*\s*[a-z]+\s*', it also doesn't find any lines.

use [[:blank:]] instead of \s, couse egrep doesn't support \s:

Code:

egrep '^\*\*\*\*[[:blank:]]+[a-z]+[[:blank:]]+Fri Jun 04'

I'm on Solaris 10, if that matters, but my egrep appears to be different from what you have.

Character classes are recognized as "[:blank:]", not "[[:blank:]]" (according to the regex(5) man page). In any case, it has no trouble recognizing "\s". I get the same results with "\s*" as I get with "[:blank:]*". I get no results with "[[:blank:]]".

To recap, I get lines with '^\*\*\*\*\s*[a-z]*\s*' and '^\*\*\*\*[:blank:]*[a-z]*[:blank:]*', but not '^\*\*\*\*[:blank:]+[a-z]+[:blank:]+', '^\*\*\*\*[:blank:]+[a-z]+[:blank:]+Fri', '^\*\*\*\*[:blank:]*[a-z]*[:blank:]*Fri', or '^\*\*\*\*\s*[a-z]*\s*Fri'.

There appear to be two issues here. One I can work around, and the other I cannot. For some reason, using "+" instead of "*" never matches. In my case, I can use "*" if I can't get "+" to work. The other issue is that adding "Fri" to the end of a working expression makes it find no lines.

try:

Code:

/usr/gnu/bin/egrep '^\*\*\*\*[[:blank:]]+[a-z]+[[:blank:]]+Fri Jun 04'

or

Code:

/usr/xpg4/bin/egrep '^\*\*\*\*[[:blank:]]+[a-z]+[[:blank:]]+Fri Jun 04'