Shell Programming and Scripting

hi,
I came accross the following script
1.var=$1
2. if [ "$var" != "" ] ; then
3. if [ "${var%${var#?}}" = "/" ] ; then
4. if [ ! -x $var ] ; then
5. return 1
6. fi
7.elif ! in_path $var $PATH ; then
8. return 2
9.fi
10. fi
here in line 3 i am getting confusion.
i am not able to understand the purpose of "${var%${var#?}}" = "/"
any help ?


cheers
RRK

"${var%${var#?}}" = "/"

It checks whether the first character is a / or not.

You need to evaluate the inner construct ${var#?} and then proceed to the outer ${var%...}

Say var=/path/to/a/dir
${var#?} returns "path/to/a/dir" i.e. it strips a single character from the front of the string and returns the rest.
${var%${var#?} would return / i.e. it strips the above resulting string from var and returns the rest which is /

Look under Parameter Expansion in the man sh