extract numbers from string in bash script

Question

My code is like this:

xinput list | grep TouchPad

then I get:

⎜ ↳ SynPS/2 Synaptics TouchPad id=14 [slave pointer (2)]

I save this output to a string variable in this way:

touchpad=$(xinput list | grep TouchPad)

So, my question is, how can I save the ID number 14 as into a number variable in the bash script? I need to use that number to turn off the TouchPad by this:

xinput set-prop 14 "Device Enabled" 0

I need to run the code automatically, so the number 14 in the above code should come from the previous code.

Thanks.

Nir Alfasi · Accepted Answer · 2015-07-08 16:08:38Z

1

num=$(echo " SynPS/2 Synaptics TouchPad id=14 [slave pointer (2)]" | grep -o '\d\d')
echo $num

OUTPUT

answered Jul 8, 2015 at 16:08

Nir Alfasi

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Comments

Jahid · Accepted Answer · 2015-07-08 16:40:04Z

0

Using Bash Parameter Expansion:

var='SynPS/2 Synaptics TouchPad id=14 [slave pointer (2)]'
num="${var/*TouchPad id=/}" # replaces ...TouchPad id= with empty string
num="${num/ */}"            # replaces space... with empty string
echo "$num"

Or

num="${var#*TouchPad id=}" # deletes ...TouchPad id= from var and assigns the remaining to num
num="${num%% *}"           # deletes space... from num

Or using grep with Perl regex:

echo "$var" |grep -oP "(?<=TouchPad id=)\d+"

edited Jul 8, 2015 at 16:40

answered Jul 8, 2015 at 16:08

Jahid

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Comments

Eugeniu Rosca · Accepted Answer · 2015-07-08 16:05:44Z

0

touchpad='SynPS/2 Synaptics TouchPad id=14 [slave pointer (2)]'
sed -r 's~.*TouchPad id=([0-9]+).*~\1~' <<< "$touchpad"
14

answered Jul 8, 2015 at 16:05

Eugeniu Rosca

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Comments

Dave · Accepted Answer · 2015-07-08 16:11:51Z

0

In your bash script:

regex="id=([0-9]+)"
[[ $touchpad =~ $regex ]]
id=${BASH_REMATCH[1]}
if [ -z $id ]; then
   echo "Couldn't parse id for $touchpad"
else
    xinput set-prop $id "Device Enabled" 0
fi

answered Jul 8, 2015 at 16:11

Dave

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