source: vendor/bash/3.1/examples/scripts/inpath

#! /bin/sh
#
# Search $PATH for a file the same name as $1; return TRUE if found.
#

command=$1
[ -n "$command" ] || exit 1

set `echo $PATH | sed 's/^:/.:/
                        s/::/:.:/g
                        s/:$/:./
                        s/:/ /g'`
        
while [ $# -ne 0 ] ; do
        [ -f $1/$command ] && exit 0    # test -x not universal
        shift
done

exit 1