quelques opérations simple avec les chaines dans #bash

${variable: ±substring}
${variable#prefixe_a_supprimer}
${variable/search/replace}
${variable//search/replaceall}

var=poete
echo ${var: -1} # affiche "e" 
echo ${var: +1} # affiche "p"
echo ${var%te}  # affiche "poe"
echo ${var#po}  # affiche "ete" 
echo ${var/t/m}  # affiche "poeme" 
echo ${var//e/3}  # affiche "po3t3"