[SOLVED] sed help

dazdaz · 07-07-2012, 05:10 PM

Code:

$ echo -en '* [[hello world1]]\n** [[hello world2]]\n'
* [[hello world1]]
** [[hello world2]]

I would like the output to be :

hello world1
hello world2

I've been working on the following regex, but for some reason, it does'nt match. I understand that * is treated as a special character in sed, which has to be escaped.

It does'nt match the 2 x **, but I don't understand why.

Code:

$ echo -en '* [[hello world1]]\n** [[hello world2]]\n' | sed 's/[\* [[|\*\* [[] (.*)\]\]/\1/g'

towheedm · 07-07-2012, 09:07 PM

According to REGEX, * is only a special character when followed by a character set.

Code:

^*    # Match any line starting with *, note it is not escaped.
[a-zA-z]*   # Here the * has the special meaning 0 or more duplicates of the char set a-z and A-Z

Code:

sed 's/[\* [[|\*\* [[] (.*)\]\]/\1/g'

Yo have specifoed a back-reference without escaping the ( or ). To do that run sed with the -r option or escape the ( and ).

Code:

sed -r 's,^[a-z]*(.*),\1,'    # or
sed 's,^[a-z]*\(.*\),\1,'

For your example, I could only get it to work with two substitute command:

Code:

echo -en '* [[hello world1]]\n** [[hello world2]]\n' | sed -e 's,^[* []*,,' -e 's,\]\+,,'

Or using the -r option to SED:

Code:

echo -en '* [[hello world1]]\n** [[hello world2]]\n' | sed -re 's,^[* []*,,' -e 's,\]+,,'

Use one substitute command:

Code:

echo -en '* [[hello world1]]\n** [[hello world2]]\n' | sed -r 's,^[* []*(.*)\]\],\1,'

Hope it helps.

grail · 07-08-2012, 04:35 AM

Code:

echo -en '* [[hello world1]]\n** [[hello world2]]\n' | sed -r 's/.*\[\[|]]$//g'
echo -en '* [[hello world1]]\n** [[hello world2]]\n' | awk -F"[][]*" '{print $(NF-1)}'

whizje · 07-08-2012, 06:08 AM

Does it have to be sed

Code:

grep -o "hello world[12]"

danielbmartin · 07-08-2012, 02:17 PM

Quote:

Originally Posted by whizje

Does it have to be sed

Code:

grep -o "hello world[12]"

I assumed that hello world represented any character string, though that was not explicitly stated. What say you, OP?

Daniel B. Martin