Shell Programming and Scripting

Try:

Code:

echo "u_sA9e-u" | grep -E '([[:space:]]|^)[a-z_][a-z0-9_-]*[$]?([[:space:]]|$)'

Thank you!

Code:

$ echo "u_sA9e-u" | grep -oE '([[:space:]]|^)[a-z_][a-z0-9_-]*[$]?([[:space:]]|$)'
$ echo "u_s9e-u" | grep -oE '([[:space:]]|^)[a-z_][a-z0-9_-]*[$]?([[:space:]]|$)'
u_s9e-u

Sorry, my mistake. somehow a superfluous caret slipped by:

Code:

grep '[ ]*[^_a-z][-_a-z0-9]*\$*[ ]*'

Code:

grep '[ ]*[_a-z][-_a-z0-9]*\$*[ ]*'

The caret means a logical NOT in this case, so in fact the meaning was inverted. ("[ab]" finds all "a"s and "b"s, ""[^ab]" finds anything except these).

Of course Scrutinizers comment about words at the beginning or end of a line is correct. I didn't intend to give a complete solution, just a hint how to construct such regexps for yourself. See also below.

In the case of your echo statement you already made sure there is a leading and a trailing blank therefore you should remove the conditionals from the word delimiters in the regexp, which makes it work:

Code:

echo " u_sA9e-u " | grep '[ ][_a-z][-_a-z0-9][-_a-z0-9]*\$*[ ]'

Scrutinizers solution is correct, but makes use of the extended regular expression syntax of the GNU-grep. This may or may not be a problem in your case. Standard POSIX-greps won't understand the pipe symbol ("|") as logical OR. If this doesn't matter in your case you should go for this solution, as it is the most comprehensive one possible.

If you would need to port the solution to different Unixes you wouldn't want to rely on this extended regular expression syntax because some "grep"s only support the standard (POSIX) features. The solution would be in this case to grep for words on the end/beginning of a line separately. The difference would be to replace the anchoring leading/trailing spaces by beginning-of-line-("^")/end-of-line-("$")-symbols.

search in the middle of the line:

Code:

grep '[ ][_a-z][-_a-z0-9][-_a-z0-9]*\$*[ ]'

search the beginning of the line:

Code:

grep '^[_a-z][-_a-z0-9][-_a-z0-9]*\$*[ ]'

search the end of the line:

Code:

grep '[ ][_a-z][-_a-z0-9][-_a-z0-9]*\$*$'

I hope this helps.

bakunin

Hi Bakunin,

The OP stated she was using GNU grep at the beginning. However please note that I suggested a general egrep solution. The Posix specification states that egrep is deprecated and that grep -E should be used instead (see grep: rationale). As such grep -E is using ERE's and certainly understands alternation, so IMO it should work with any Posix-compliant grep.

S.

I have overlooked the O/Ps requirement, but saw it now, as you mentioned it. The information about EREs in POSIX was news to me, thanks for the info. I stand corrected.

bakunin