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shogun1234

10-03-2009 10:46 PM

Pattern search question in shell

I read a webpage - http://promberger.info/linux/2009/01...shell-scripts/

and would like to search functions which contains fromMessage and toMessage.

Then I try the command

Code:

cat target | grep $from\|to$Message

This would cause nothing to return

Code:

cat target | grep (from|to)Message

This would cause "bash: syntax error near unexpected token `from'"

Code:

cat target | grep \[from\|to\]Message

This would return

Code:

fromMessage

toMessage

PersistMessage

What function I need to use so that I can get the following result?

Code:

fromMessage

toMessage

Below is the target file content:

Code:

fromMessage



toMessage





abcMessage



Message



PersistMessage

Thanks for help.

slakmagik

10-03-2009 11:07 PM

You need to quote parentheses from the shell and use egrep for alternatives and don't need cat:

egrep '(from|to)Message' target

-- Well, you can use

grep '$from\|to$Message' data

but I don't recommend it. A lot easier to prefix 'e' or use the extended switch and be more standard at the same time.

lutusp

10-03-2009 11:09 PM

Quote:

Originally Posted by shogun1234 (Post 3706726)

I read a webpage - http://promberger.info/linux/2009/01...shell-scripts/

and would like to search functions which contains fromMessage and toMessage.

Then I try the command

Code:

cat target | grep $from\|to$Message

This would cause nothing to return

Code:

cat target | grep (from|to)Message

This would cause "bash: syntax error near unexpected token `from'"

Code:

cat target | grep \[from\|to\]Message

This would return

Code:

fromMessage

toMessage

PersistMessage

What function I need to use so that I can get the following result?

Code:

fromMessage

toMessage

Below is the target file content:

Code:

fromMessage



toMessage





abcMessage



Message



PersistMessage

Thanks for help.

Do it this way:

Code:

$ grep -P "(from|to)Message" < target

And read:

Code:

$ man grep

syg00

10-03-2009 11:10 PM

Your first one is closest to working - try it as

Code:

grep "$from\|to$"Message target

- note "cat" not required.
Better is to use egrep and avoid the escapes altogether -

Code:

grep -E "(from|to)"Message target

kirukan

10-03-2009 11:13 PM

Try this
cat target | egrep "(from|to)"Message

catkin

10-04-2009 03:43 AM

Quote:

Originally Posted by syg00 (Post 3706747)

Your first one is closest to working - try it as

Code:

grep "$from\|to$"Message target

- note "cat" not required.
Better is to use egrep and avoid the escapes altogether -

Code:

grep -E "(from|to)"Message target

All good but single quotes are the best choice because nothing (absolutely nothing) between the opening and closing single quotes is touched by the shell. Leaves you with this as the most minimal solution

Code:

egrep '(from)|(to)Message' target

Good practice (saves brain work and complexifusion): use single quotes whenever you don't need double quotes.

slakmagik

10-04-2009 04:08 AM

That would also match 'from', if it was in the data, though.

catkin

10-04-2009 04:19 AM

Quote:

Originally Posted by slakmagik (Post 3706944)

That would also match 'from', if it was in the data, though.

Oops! So it would and thank you for pointing it out. This is better

Code:

egrep '((from)|(to))Message' target

slakmagik

10-04-2009 04:29 AM

Sure thing. :) But

Code:

egrep '(from|to)Message' target

would also work.

catkin

10-04-2009 06:58 AM

Quote:

Originally Posted by slakmagik (Post 3706971)

Sure thing. :) But

Code:

egrep '(from|to)Message' target

would also work.

And so much neater, too :)

shogun1234

10-10-2009 09:17 AM

I read the manual and at the moment using

Code:

grep -E '(from|to)'Message text.txt

looks working fine for me.

Thanks all your help.

Those information are really helpful.

I appreciate it.: )

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