Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
No Plan.
vrfy
Out of security considerations, many networks disable finger and its associated daemon. [32]
Verify an Internet e−mail address.
Remote Host Access
sx, rx
sz, rz
ftp
cu
uucp
telnet
wget
lynx
rlogin
rsh
The sx and rx command set serves to transfer files to and from a remote host using the xmodem
protocol. These are generally part of a communications package, such as minicom.
The sz and rz command set serves to transfer files to and from a remote host using the zmodem
protocol. Zmodem has certain advantages over xmodem, such as greater transmission rate and
resumption of interrupted file transfers. Like sx and rx, these are generally part of a communications
package.
Utility and protocol for uploading / downloading files to / from a remote host. An ftp session can be
automated in a script (see Example 17−7, Example A−5, and Example A−14).
Call Up a remote system and connect as a simple terminal. This is a sort of dumbed−down version of
telnet.
UNIX to UNIX copy. This is a communications package for transferring files between UNIX servers.
A shell script is an effective way to handle a uucp command sequence.
Since the advent of the Internet and e−mail, uucp seems to have faded into obscurity, but it still exists
and remains perfectly workable in situations where an Internet connection is not available or
appropriate.
Utility and protocol for connecting to a remote host.
The telnet protocol contains security holes and should therefore probably be avoided.
The wget utility non−interactively retrieves or downloads files from a Web or ftp site. It works well
in a script.
wget −p http://www.xyz23.com/file01.html
wget −r ftp://ftp.xyz24.net/~bozo/project_files/ −o $SAVEFILE
The lynx Web and file browser can be used inside a script (with the −dump option) to retrieve a file
from a Web or ftp site non−interactively.
lynx −dump http://www.xyz23.com/file01.html >$SAVEFILE
Remote login, initates a session on a remote host. This command has security issues, so use ssh
instead.
Remote shell, executes command(s) on a remote host. This has security issues, so use ssh
Chapter 12. External Filters, Programs and Commands 193