NAME¶asp - find an host IP address by its name
SYNOPSIS¶asp [-uv] [-f | [-d dir] [-e ext]] [-a addresses] [-r repetitions] [-s send_delay] [-w wait_time] [-p port] hostname
DESCRIPTION¶Asp finds the IP address of an Internet connected host. In order to find it, the peer hostname (not the FQDN), and the range of its possible IP addresses need to be specified. Those IP addresses could be simple IP addresses as 127.0.0.1 or "metaip" addresses as 127.0.0.1-20 or 127.0.0.*: the former is a simple way to avoid to type a lot of consecutive addresses, the latter is short for 127.0.0.1-254.
In order to simplify the management of the associations between hostnames and addresses, asp searches in a specified directory a text file containing the possible IP addresses of the looked for host. The name of the text file has to be formed by the hostname followed by an optional extension of your choice.
For example to find the author's dynamic IP address, obviously if I am on line, you can provide my metaip address on standard input with the command:
22.214.171.124-18" | asp -f atomic
or you can put my metaip address in a file called atomic in your ~/.asp directory, like this:
126.96.36.199-18" > ~/.asp/atomic
and then you can simply do:
- Update the file /etc/hosts with the IP address of hostname or delete the possible old entry if the address is not found. Obviously the file have to by writable by the user.
- Include more verbiage to make output readable by humans. Default consists only of dotted quad IP address, which is intended for output substitution in scripts.
- Force the reading of addresses from standard input instead that from the hostname's file.
- -d dir
Set the directory containing the addresses file referred by hostname to dir. Default is ~/.asp.
- -e ext
Set addresses files extension to ext. Default is no extension.
- -a addresses
Set the number of queries to send before make a pause of send_delay seconds. Default is 12 queries.
- -r repetitions
Set the number of times to try the same address. Default is 3 times.
- -s send_delay
Delay the sending of the next group of addresses send_delay seconds. Default is 2 seconds.
- -w wait_time
Wait the peer reply for wait_time seconds. Default is 5 seconds.
- -p port
Specify an alternative port number. For default the port number is obtained searching the asp entry in /etc/services.
- Show version information.
- This variable could be used to store your preferred settings. An option set in this environment variable could be overridden or toggled from command line.
BUGS¶UDP is an unreliable protocol, therefore there is a chance you will not find the host even if it is on line. Anyway, if you are sure that the peer is on line and asp aware, you could adjust the various parameters until you get a reply. At last you will find the correct settings for your particular needs. This until the RDM communication style will be implemented under Linux.
Obviously the hostname has to be unique among the possible IP addresses: asp will hook to the first correct reply.
AUTHOR¶Stenio Brunetta <email@example.com>
Comments and suggestions are welcome.
ACKNOWLEDGMENTS¶Steven N. Hirsch <firstname.lastname@example.org> for v1.3 bug fix and for the verbose option.
Colin Phipps <email@example.com> for the tmpnam security issue.