inpath

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

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

    cmd=$1
    ourpath=$2
    result=1
    oldIFS=$IFS
    IFS=":"

    for directory in "$ourpath"
    do 
        if [ -x $directory/$cmd ]; then
            result=0    # If we're here, we found the command
        fi  
    done

    IFS=$oldIFS
    return $result
}

checkForCmdInPath()
{
    var=$1

    if [ "$var" != "" ]; then
        if [ "${var:0:1}" = "/" ]; then
            if [ ! -x $var ]; then
                return 1
            fi
        elif ! in_path $var "$PATH" ; then
            return 2
        fi
    fi
}

if [ $# -ne 1 ]; then
    echo "Usage: $0 command" >&2
    exit 1
fi

checkForCmdInPath "$1"
case $? in 
    0 ) echo "$1 found in PATH" ;;
    1 ) echo "$1 not found or not executable" ;;
    2 ) echo "$1 not found in PATH" ;;
esac

exit 0