I am looking into the code displayed below and it checks the input if the row/column arguments start with either -r or -c. What does ${1:0:2} mean in this context? rowArgName=-rcolArgName=-cif [ ${1:0:2} != $rowArgName ] && [ ${1:0:2} != $colArgName ]then   echo $correctCmdMsg >&2   exit 1fi
What does ${1:0:2} mean in this context?
bash;shell script