#!/bin/sh
# inpath - Verifies that a specified program is either valid as is,
# or that it can be found in the PATH directory list.

in_path()
{
    # Given a command and the PATH, try to find the command. Returns
    # 0 if found and executable, 1 if not. Note that this temporarily modifies
    # the IFS (input field separator) but restores it upon completion.

    cmd=$1 path=$2 retval=1
    oldIFS=$IFS IFS=":"

    for directory in $path
    do  
        if [ -x $directory/$cmd ] ; then
            retval=0 # if we're here, we found $cmd in $directory
        fi  
    done
    IFS=$oldIFS
    return $retval
}

checkForCmdInPath()
{
    var=$1

    # The variable slicing notation in the following conditional
    # needs some explanation: ${var#expr} returns everything after
    # the match for 'expr' in the variable value (if any), and
    # ${var%expr} returns everything that doesn't match (in this
    # case, just the very first character. You can also do this in
    # Bash with ${var:0:1}, and you could use cut too: cut -c1.

    if [ "$var" != "" ] ; then
        if [ "${var%${var#?}}" = "/" ] ; then
            if [ ! -x $var ] ; then
                return 1
            fi  
        elif ! in_path $var $PATH ; then
            return 2
        fi  
    fi  
}