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.

Answer 1

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

<强>输出

14

Answer 2

$_

Answer 3

使用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"

或

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

或者将grep与Perl正则表达式一起使用：

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

Answer 4

在你的bash脚本中：

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