126. The Power of the Command
Line
By Andrew D. Wright
Blank, mysterious, powerful, it's the common link between all major
operating systems. The command line makes most people nervous.
People are more familiar with point and click programs for most of their
computing needs. However, buried at the heart of Windows, of Macintosh OS
X, of Linux and Unix is the command line, holdover from the olden days of
computing.
In Windows, go to the Start menu then Run then type in: cmd and hit
OK to
open a command line window.
To use the command line you type in a command and hit enter. The computer
will then look for a program with the name you typed and run the program.
The folders where the computer will look for the program are called the
path. The path is an environmental variable, which means it can be altered
or added to by the user.
You can set the path by clicking Start then right clicking on My Computer
and selecting Properties. Click on the Advanced tab and the Environmental
Variables button. Under System variables will be the path. Double click on
it to edit it. Folders are separated by semi-colons.
I usually create a folder called Batch on my C: drive and make a path to
it. Any new command line programs I get I put in this folder so I can run
them from any command prompt in any folder.
You can run a program from the command line if you are looking at the
folder the program is in, or if the folder is listed in the path. Most
programs that can be run from the command line have switches that will
make the program do different things. One of the most common switches is
for help with a program, usually a listing of the available switches and
what they do.
To use the help switch, type in a command, put in a space then type
/? and hit enter.
A common command line use is to diagnose an internet connection problem. A
good way to do this is to ping a server, which means sending it a data
packet and getting it back. I like to use the Chebucto Community Net
server for this, since it is a long-standing machine name on the internet
and it has a catchy easy to remember IP address.
The first thing to try is to ping the server. To do this type:
ping chebucto.ca
The response should look like this:
Pinging chebucto.ca [192.75.95.75] with 32 bytes of data:
Reply from 192.75.95.75: bytes=32 time=18ms TTL=250
Which tells us the computer can successfully look up the domain and
communicate with it. If this doesn't work, then maybe the IP address could
be pinged: ping 192.75.95.75
If this gets a reply where the domain name didn't, then it means the
computer cannot reach a DNS domain name lookup server, usually due to
over-zealous firewall settings.
Another handy networking command is ipconfig, which will show you
information on your network adapters. Use the /all switch for
detailed information, use the /renew switch to reset network
connections and of course, the /? switch for more options and help.
Commands can be put together so that one program can run after another, or
based on what the first program did, a different program might be run
instead. These combinations of commands are called batch files. They are
really just text files made executable with the .BAT file name extension.
Batch files can be used to automate a sequence of frequently run programs
among other things.
Long-time Chebucto Community Net contributor and Userhelp volunteer
Richard Bonner has put together a popular and heavily visited guide to the
command line online.
http://www.chebucto.ns.ca/~ak621/DOS/
The Mousepad runs every two weeks. It's a service of Chebucto Community
Net, a community-owned Internet provider. If you have a question about
computing, email mousepad@chebucto.ns.ca or
click here. If we use your question
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Originally published 22 February 2008
