The Best Internet Programs/BESTINTERNET.bin/internet/lrn_inet/li_unix.txt

Text File | 1994-10-05 | 7.4 KB | 171 lines

 Unix

Most Internet host computers use Unix as their operating
system, so a knowledge of certain Unix commands is essential
for managing your Internet sessions and the files in your
Unix home directory.  Even if your Internet provider offers
a fancy graphical interface, it will not be long until you
telnet to another network where you will have to work with
the bare Unix prompt, so it is good to know a little Unix.

Unix is very complex, and is definitely NOT user friendly.
It was written by programmers for programmers.  Nevertheless
this lesson will teach you basic facts about several basic
commands that you will find very valuable.

 ls - Listing Your Files

To learn what files are in your home directory enter the
command ls.  As with all Unix commands you must use lower
case letters.  A list of file names, alphabetized, will
appear on your screen.  Most Unix commands allow you to
enter a "switch" after them, to affect the way the command
works or to format it's output.  The command ls -l will
produce a "long" list of your files, showing file attributes,
creation dates, file size, and name.  The dash (-) before the
letter l tells Unix that this is a switch.  The command
ls -a shows "all" files, including hidden ones, in your
directory.  The command ls -la shows all files in long form.
The equivalent DOS command is "dir."

 cp - Copy A File

To copy a file enter the command: cp file1 file2, where file1
is the name of the file you want to copy and file2 is the name
you want to assign to the copy.  After executing this command
you will have two copies of the file called file1, one named
file1 and one named file2.  Unix does not check to see if
another file with the name of file2 exists prior to executing
this command, so be very careful.  If a file called file2
existed before executing the above command, it would be over-
written with the contents of file1.  Unix also operates on the
principle that "no news is good news."  It will not inform you
when it successfully carries out the command.  The equivalent
DOS command is "copy."

 mv - Renaming Or Moving A File

The command mv file1 file2 will change the name of file1 to
file2.  Be very careful, though.  If file2 already exists
it will be overwritten with the contents of file1 and Unix
will not warn you.

The mv command is very powerful because it can be used to
move files between directories also.  mv is a combination
of the DOS commands "rename" (ren) and "move."





 rm - Removing Files

The command rm file1 will delete (remove) the file named
file1.  Be extremely cautious, in Unix there is no command
equivalent to the DOS undelete command.  Once your file has
been deleted there is no way to get it back.  When it's gone,
it's gone for good.

With copying, deleting and listing commands you may also use
wildcard symbols as you would in DOS.  The "?" wildcard acts
just like it does in DOS, substituting for a single character
in a file name.  The "*" symbol, however, is more powerful.
The command ls f* would list all files beginning with "f."
The command rm * would delete all files in your directory.

 cat - Viewing A File

To view the contents of a text file use the command cat file1,
where file1 is the name of the file you want to view.  The
contents of the file will scroll quickly over your screen.  If
the file is longer than will fit on a single screen, use the
"more" filter along with cat, like this: cat file1 |more.  The
vertical bar before "more" is called the piping symbol, and
"pipes" the output of the cat command to the paging command
"more."  In this case, you will see a screenful of information
at a time.  Pressing the spacebar will advance to the next
screen.  Pressing control-c will break out of the more filter.
The cat is only for text files, not binary files.  The equiv-
alent DOS command is "type."

 cd - Changing Directories
The Unix file system is similar to the DOS system (DOS stole
the idea from Unix).  It uses a single root directory and a
system of "tree" directories branching off from the root.
The directories below a directory are called sub-directories.
The equivalent Mac terminology is folders and folders within
folders.  For example, your home directory may be called
/pub/guests/efudd.  (Notice the Unix slashes go the opposite
direction from the DOS slashes).  To change to a subdirectory
called News beneath your home directory enter the command:
cd News.  To change to the directory above your home directory
enter: cd .., where the two dots are an abbreviation for "the
directory above."  To change from the root directory to your
home directory enter: cd /pub/guests/efudd.

 man - Getting Help

There is an on-line help facility on every Unix system called
man (short for manual).  To get help on any Unix command
enter: man [commandname].  For example, to get help on the ls
command enter: man ls.  Be prepared for some heavy sledding,
though.  The manual pages are very technical and go into pain-
ful detail about the implications of every switch available to
every command.  This is what you want in a technical manual,
but it is not easy to get a short, simple answer to a simple
question--but we warned you, Unix is not user friendly.

The equivalent DOS command is "help."


 sz - Downloading/Uploading Files
If you dial in to Internet you will soon need to know how to
get files from your Unix home directory (where they will go
when you ftp them) to your home PC.  What you do is use a
file transfer protocol supported by your communications pro-
gram.  The best is Zmodem, but if your program does not
support Zmodem use Kermit (next screen).  The key to Down/Up-
loading is to set up the host Unix system first, and then
begin the command from your PC.  For example, to download the
file file1.zip from your home directory enter the command:
sz -b file1.zip, then issue the command that initiates Zmodem
file transfers from your communications program.  (Your pro-
gram may do this automatically).  The "-b" means binary file.
To upload, begin with the Unix command rz -b file1.zip.

 kermit - A Slower But More Reliable Alternative

If Zmodem will not work for you you can always use the kermit
protocol, which is almost universally supported.  To download
using kermit first start the kermit program on your Unix host
by entering the command: kermit.  After the kermit> prompt
appears, enter the command: set file type binary (if you are
transferring a binary file).  Then issue the command send
file1.zip.  Then from your own communications program issue
the command that initiates a kermit download.  Be sure the
file type parameter is set correctly on your end too.  To
upload the procedure is the same, except begin with the
Unix kermit command: receive file1.zip.  To exit from the
Unix kermit program enter: quit, or q at the kermit prompt.

 Summary

This is just the barest introduction to Unix commands, but
they are definitely the most essential commands.  If you do
not know them life with Unix will be very difficult.  The
printed summary to this lesson lists a couple of excellent
references to Unix if you wish to know more.

If you are a Mac or Windows user exclusively, you will find
this daunting, and even if you are used to working from the
DOS C:> prompt you will find Unix difficult at first, but
it just takes a little practice.  Good luck!