Shell Programming and Scripting

${parameter/pattern/string}
The pattern is expanded to produce a pattern just as in pathname expansion. Parameter is expanded and
the longest match of pattern against its value is replaced with string. If Ipattern begins with /, all
matches of pattern are replaced with string. Normally only the first match is replaced. If pattern
begins with #, it must match at the beginning of the expanded value of parameter. If pattern begins
with %, it must match at the end of the expanded value of parameter. If string is null, matches of
pattern are deleted and the / following pattern may be omitted. If parameter is @ or *, the substitu-
tion operation is applied to each positional parameter in turn, and the expansion is the resultant
list. If parameter is an array variable subscripted with @ or *, the substitution operation is applied
to each member of the array in turn, and the expansion is the resultant list.