Ubuntu – extract number from a string

bash

i have the following string

Device Enabled (126):   1

can i extract in a variable VAR only 126 and NOT (126) ?

p.s 126 = random number

please help me !

EDIT
i paste my script so u can understand the solution

ID=`xinput list | grep -i TouchPad | awk -F= '{ print $2}' | awk '{print $1}'`
VALOREENABLE=`xinput list-props $ID | grep -i Enabled |awk '{print $3}'`
VALORESENSE=`xinput list-props $ID | grep -i Profile |awk '{print $3}'

in my case VALOREENABLE = (126)
and VALORESENSE (256) i want 126, 256 only without () :(`

Best Answer

echo "Device Enabled (126):   1" | grep -P -o "[0-9]+" | head -1

echo puts your string into the pipe
that goes to grep, which is a program to apply regular expressions. The option -P enables PEARL like behaviour (which enables you to use the +), and the -o tells grep to only output the matching part of the string. Each match will be printed to a new line
use head to pick the line you want. Since we want the first number, we will pick the first line. If you were interested in the one, you would do head -2.

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Answering to the third question: of course it can be used meaningfully in the way at Bash manual clearly hints – in a trap, e. g.:

$ trap 'echo ‘$BASH_COMMAND’ failed with error code $?' ERR
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fgfdjsa: command not found
‘fgfdjsa’ failed with error code 127
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Ubuntu – Extract word from string using grep/sed/awk

You can use grep with PCRE (-P):

grep -Po 'spring.profiles.active=\K[^ ]+' <<<'.....string.....'

spring.profiles.active= will match this substring literally, \K will discard the match
[^ ]+ will select the desired portion i.e. the portion after spring.profiles.active=, till the next space

For a file:

grep -Po 'spring.profiles.active=\K[^ ]+' file.txt

Example:

% grep -Po 'spring.profiles.active=\K[^ ]+' <<<'00:28:04 /usr/lib/jvm/jre/bin/java -DJDBC_CONNECTION_STRING= -Dspring.profiles.active=qa -XX:MaxPermSize=256'
qa

sed would take similar logic:

sed -r 's/.*spring.profiles.active=([^ ]+).*/\1/' <<<'.....string.....'

Example:

% sed -r 's/.*spring.profiles.active=([^ ]+).*/\1/' <<<'00:28:04 /usr/lib/jvm/jre/bin/java -DJDBC_CONNECTION_STRING= -Dspring.profiles.active=qa -XX:MaxPermSize=256'
qa

Handling errors:

In your script you may want to handle the case where there is no match, in other words where your original string does not contain spring.profiles.active=. In the above sed example, you obtain the whole original string, which could create problems:

% var="$(sed -r 's/.*spring.profiles.active=([^ ]+).*/\1/' <<<'00:28:04 /usr/lib/jvm/jre/bin/java -DJDBC_CONNECTION_STRING= -XX:MaxPermSize=256')"
% echo $var
00:28:04 /usr/lib/jvm/jre/bin/java -DJDBC_CONNECTION_STRING= -XX:MaxPermSize=256

If you prefer to obtain the empty string when there is no match, add the -n option to the sed command and the p option to the sed s command, like this:

% var="$(sed -rn 's/.*spring.profiles.active=([^ ]+).*/\1/p' <<<'00:28:04 /usr/lib/jvm/jre/bin/java -DJDBC_CONNECTION_STRING= -XX:MaxPermSize=256')"
% echo $var

% var="$(sed -rn 's/.*spring.profiles.active=([^ ]+).*/\1/p' <<<'00:28:04 /usr/lib/jvm/jre/bin/java -DJDBC_CONNECTION_STRING= -Dspring.profiles.active=qa -XX:MaxPermSize=256')"
% echo $var
qa

Then you can test if $var is empty or not.

Best Answer

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