Solution

#!/bin/bash
function limitSubStringLenght {
 # 1ドル => main string
 # 2ドル => substring pattern (regex)
 # 3ドル => max lenght
 work="1ドル"
 while IFS= read -r result
 do
 # $result contain substring matched
 # save a copy of the cuted version of the substring
 endCut=$(echo $result | cut -c 1-"3ドル")
 # cut the substring in the main string
 work=$(echo -n "$work" | sed "s#$result#$endCut#g")
 # we set the substring to match here
 done < <(echo "1ドル" | grep -Eo "2ドル")
 echo -n "$work"
}
 # set the example variable
diskInfos=$(echo -n '[fuser.sshfs] /media/partition/blablabla 1.2GB / 2.4GB')
 # displaying test example before change it
echo ' BEFORE => '"$diskInfos"
 # apply change and save it in to $diskInfos
diskInfos=$(limitSubStringLenght "$diskInfos" '(/[a-Z0-9._]{1,}){1,}/{0,}' 20)
 # displaying results
echo -n ' AFTER_ => '"$diskInfos"

Ce qui produit :

└─ $ ▶ ./test.bash 
 BEFORE => [fuser.sshfs] /media/partition/blablabla 1.2GB / 2.4GB
 AFTER_ => [fuser.sshfs] /media/partition/bla 1.2GB / 2.4GB

Enjoy 😉