ksh construct

Shell Programming and Scripting
1

Hi Guys,

could someone tell me what this ksh construct does

typeset -r PROG_PWD=${0%/*} does

I understand the -r for readonly but I would very much appreciate a definitive account of what this will set $PROG_PWD to.

If I run this at the cmd line it it gets set to /usr/bin but I would like to know .....why?

cheers

2

sorry - there is an extra 'does' in the post...

ignore the one on the 'typeset' line

cheers

3

From the ksh man page:

${parameter%word}       Remove Smallest Suffix Pattern.  The
                             word   is   expanded  to  produce  a
                             pattern.  The  parameter   expansion
                             then  results in parameter, with the
                             smallest  portion  of   the   suffix
                             matched by the pattern deleted.

Suppose $0 is /usr/bin/ksh, then ${0%/} means that the / is expanded to /ksh - this is the smallest pattern that you can get, and it is deleted. If you had %%/*, it would be the largest match to the pattern, which would mean /usr/bin/ksh (the output would be nothing).