I have a bash script to control Linux perf. As you may know, perf takes core list which can be specified in 1 of the three ways.
Currently, I have an environment variable CORENO which will control -C$CORENO.
However, I need to offset CORENO by a fix offset (I.e.2)
I could do ((CORENO+=2)) but that only work for case 1.
Is there a Linux/bash trick to allow me to apply fix offset to every number in a bash variable?
Since you're on Linux, here's some GNU sed:
addtwo() {
sed -re 's/[^0-9,-]//g; s/[0-9]+/$((\0+2))/g; s/^/echo /e;' <<< "$1"
}
addtwo "1"
addtwo "1-4"
addtwo "3,4,5"
It will output:
3
3-6
5,6,7
It works by replacing all numbers with $((number+2)) and evaluating the result as a shell command. A whitelisting of allowed characters is applied first to avoid any security issues.
Take a look at seq
for core in `seq 2 10`; do
echo CORENO=$core
done
I’ve upvoted the sed-based answer from @that other guy because I like it more than mine, which is a “pure bash” solution, consisting of a recursive function.
function increment () {
local current="$1" n=$(($2))
if [[ "$current" =~ ^[0-9]+$ ]]; then
echo $((current+n))
elif [[ $current == *,* ]]; then
echo $(increment ${current%%,*} $n),$(increment ${current#*,} $n)
elif [[ $current == *-*-* ]]; then
echo ERROR
elif [[ $current == *-* ]]; then
echo $(increment ${current%-*} $n)-$(increment ${current#*-} $n)
else
echo ERROR
fi
}
CORENO=3-5
CORENO=$(increment $CORENO 2)
echo $CORENO
increment 3-5,6-8 3
My function will print ERROR when given an illegal argument. The one from @that other guy is much more liberal...
