Don't need the whole line, just the match from regular expression
Solution 1:
Use the -o
option in grep
.
Eg:
$ echo "foobarbaz" | grep -o 'b[aeiou]r'
bar
Solution 2:
2 Things:
- As stated by @Rory, you need the
-o
option, so only the match are printed (instead of whole line) - In addition, you neet the
-P
option, to use Perl regular expressions, which include useful elements like Look ahead(?= )
and Look behind(?<= )
, those look for parts, but don't actually match and print them.
If you want only the part inside the parenthesis to be matched, do the following:
grep -oP '(?<=\/\()\w(?=\).+\/)' myfile.txt
If the file contains the sting /(a)5667/
, grep will print 'a', because:
/(
are found by\/\(
, but because they are in a look-behind(?<= )
they are not reporteda
is matched by\w
and is thus printed (because of-o
))5667/
are found by\).+\/
, but because they are in a look-ahead(?= )
they are not reported
Solution 3:
sed -n "s/^.*\(captureThis\).*$/\1/p"
-n don't print lines
s substitute
^.* matches anything before the captureThis
\( \) capture everything between and assign it to \1
.*$ matches anything after the captureThis
\1 replace everything with captureThis
p print it
Solution 4:
Because you tagged your question as bash in addition to shell, there is another solution beside grep :
Bash has its own regular expression engine since version 3.0, using the =~
operator, just like Perl.
now, given the following code:
#!/bin/bash
DATA="test <Lane>8</Lane>"
if [[ "$DATA" =~ \<Lane\>([[:digit:]]+)\<\/Lane\> ]]; then
echo $BASH_REMATCH
echo ${BASH_REMATCH[1]}
fi
- Note that you have to invoke it as
bash
and not justsh
in order to get all extensions $BASH_REMATCH
will give the whole string as matched by the whole regular expression, so<Lane>8</Lane>
${BASH_REMATCH[1]}
will give the part matched by the 1st group, thus only8
Solution 5:
If you want only what is in the parenthesis, you need something that supports capturing sub matches (Named or Numbered Capturing Groups). I don't think grep or egrep can do this, perl and sed can. For example, with perl:
If a file called foo has a line in that is as follows:
/adsdds /
And you do:
perl -nle 'print $1 if /\/(\w).+\//' foo
The letter a is returned. That might be not what you want though. If you tell us what you are trying to match, you might get better help. $1 is whatever was captured in the first set of parenthesis. $2 would be the second set etc.