Telnet was big back in the old days
(1994). Most isp's offered TELNET/SHELL access as a standard feature in a
webhosting package. Gradually this has began to disappear because it
takes a lot more monitoring of web servers to maintain security on servers
where users have REAL (non-virtual) accounts. This cuts into ISP
profits and thus today you have many huge, generic ISP clones that rely on
software as their only means of security and have substituted weak
interfaces such as web-shells and cgi-wrappers for the real thing.
This is about like confusing a garden burger for a filet mingon.
Telnet is by far the MOST POWERFUL interface you can have into a web
server. Telnet is not available for NT users but is available on
some of the better hosting companies.
Whenever you CONNECT to a server you use
what is called a PROTOCOL. There are SEVERAL protocols. Some
of which you are already familiar with. Here is a list of the ones
you will be concerned with:
Most servers accessed through telnet
will be using the unix operating system. This section contains a sub set
of unix commands useful for navigating the system and managing files. The
command descriptions use the following format
command - use
- invocation with arguments and useful
options
Examples
cd - change directory
- cd directory
Changes current directory to a new
directory.
- cd
- This returns you to your home
directory.
- cd ..
- This moves you up one level in the
directory hierarchy.
- cd work
- This moves you to the subdirectory
work within the current directory.
- cd ~/mystuff
- This moves you to a subdirectory
mystuff within your home directory.
- cd /usr/users/joe/stuff
- This moves you to a subdirectory
stuff in Joe's home directory..
chmod - change access permission (mode) of a file
- chmod mode filename
Changes the file-access permission for
the specified file(s) to the specified permission(mode).
There are two ways to change permissions: through symbolic or numeric
form. Numeric form is described here. A file is assigned a numeric
"mode" that is the sum of all modes associated with the file.
The modes are as follows:
400 - owner has read permission
200 - owner has write permission
100 - owner has execute permission
040 - group has read permission
020 - group has write permission
010 - group has execute permission
004 - world has read permission
002 - world has write permission
001 - world has execute permission
The lowest possible mode value is 000 - which means no one can read,
write, or execute the file. The highest possible value is 777 - which
means everyone can read, write and execute the file.
- chmod 777 notes
- The owner can read, write and
execute notes. The files specified group and all other users may
only read the file.
ls - list files
- ls options directory
Lists the contents of the specified
directory. If no directory is specified, the contents of the current
directory are listed.
- ls
- Lists the contents of the current
directory.
- ls -l
- Lists the contents of the current
directory in long form - shows file-access permissons, owner, etc.
- ls -a
- Lists the contents of the current
directory including hidden ( dot files like .htaccess) files.
- ls -al
- Lists the contents of the current
directory in long form including hidden files.
- ls -t /user/user/joe
- Lists the contents of the Joe's
directory by time stamp.
mkdir - make directory
- mkdir options directory
Creates a new directory.
- mkdir test
- Creates a new directory called
test.
- mkdir -m 744 work
- Creates a new directory called work
with permissions set to 744.
perl - invoke perl
- perl filename
- perl testscript.pl
- Invokes the perl interpreter for
the file testscripts.pl.
- /usr/local/bin/perl testscript.pl
- Invokes the perl interpreter
located at /usr/local/bin/perl for the file testscripts.pl.
pwd - print working directory
- pwd
Prints the full path of the current
working directory.
rm - remove file
- rm options files
Removes files, providing you are the
owner of the file or have write permission to the directory containing
the file. This command can also be used to delete directories.
Note: Use this command with caution.
When a file is removed, it is really gone. It does not go to a recycle
bin or waste basket.
- rm test
- Removes the file named test.
- rm *
- Removes all files in the current
directory.
- rm -r stuff
- Removes a directory named stuff and
all it's contents, including files and subdirectories.
- rm -i
- Removes files after verification from
user.
tar - archive/dearchive files
- tar function options file
Writes files to an archive or extracts
files from an archive depending on how the command is configured.
Technically tar stands for tape archiver because originally most
archives were stored to tape. However, tar writes to and extracts from
hard disks and diskettes as well as tape. The archive referred to by tar
is, in fact, a file itself, similar to a zip file.
Note that tar is slightly different than other unix commands because it
has two sets of options - a function option followed by another set of
options. The most often used functions are:
c - create a new tar archive
x - extract files from within a tar archive
The most commonly used options are:
v - verbose mode
f - specify device (or file) to archive to or extract from.
- tar xvf codegame.tar
- Extracts all of the files in the
archive codegame.tar using verbose mode (prints a record).
- tar cf backup.tar /user/users/joe
- Creates a new archive named
backup.tar of all the files in the directory /user/users/joe.
which - which file corresponds to a command
- which command
List which file corresponds to the
specified command.
- which perl5
- Displays the file path to perl5.
i.e: /usr/bin/perl
