se percent signs follow numbers.
The expression ${DIRSTACK :-$PWD} evaluates to $DIRSTACK if it is non-null or $PWD (the current directory) if it is null.
Table 4.1: Substitution Ope... ss rather than within the shell. Another utility, dirname(1), does essentially the opposite of basename: it returns the directory prefix only. It is equivalent to the Korn s... within the "back tick" shell operators like TARGETDIR=`dirname $1`. The "back tick" operators are equivalent... expressions:
path = ${foo%/*}
To get: /tmp/my.dir (like dirname)
file = ${foo##*/}
To get: filename.tar.g
