Anything appearing in italic, like this is either an executable command or emphasized text. Tools (executable commands) are in italics to prevent confusion. Some tools have names which are real english words, such as the “locate” tool.

Are represented by using a '-' (dash sign) in-between the key(s), which must be used in combination. All combinations are also printed in italics to improve clarity. For example CTRL-Z means hold down the Control key and press the z key.

Admonitions are little pictures used to emphasize something of importance to the reader.

The five types used are:

	This is a note
	Notes often give important information about a tool.

	This is a tip
	This will offer a useful switch or useful way to use a tool.

	This is something important
	This is something that is considered very important. Consider it like a note with extra importance, they are usually there to save the reader time.

	This is a caution
	This will inform you of something that you be careful about (because it could be harmful to your system).

	This is a warning
	This will inform you of something that you shouldn't do (because it probably will break something within your system).

Code examples are shown for most commands.

Below is an example of what code looks like:

Hello World, I'm a code example. :)

(or a similar phrase) simply shows how you would normally use the command. Often real examples are used instead of explaining the command syntax.

The phrase “ Command syntax” is always followed by the way you would type a command in a shell.

The standard syntax for any tool is usually:

command -options file

	Note
	Note that some tools do not accept options.

Also note that most commands, even when not explicitly stated, will work with standard wildcards (or globbing patterns) such as *, [A-Z] and various other standard wildcards. Refer to Section 20.4.1 for further information.

Access keys enable navigation through the document, without relying on a mouse. The following keys have been given special meaning in this document:

If you also happen to be reading the document from its original location, then the following access keys can also be used:

Chris allowed the use of his lyxtox scripts to convert the LyX file of the document to working DocBook SGML output (to learn how to use the lyxtox scripts yourself, see Document processing with LyX and SGML).

• Chris provided useful suggestions and advice, and added an index listing for many of the commands.

• Chris is also responsible for the great looking HTML file for this document (the CSS file and HTML customisations are completely his work).

• Chris has also helped fix up problems in the document (many times), especially with docbook/sgml, and LyX related issues.

• Chris has also improved the structure of the document by adding labels and fixing minor errors.

William provided a thorough review of the document as required by the Linux Documentation Project. He is responsible for a variety of improvements to the quality of this document.

His contributions include:

• Improvements to the readability of this document.

• Improvements to the structure and consistency of this document.

• Various grammar improvements throughout the document.

• Repair of some minor technical errors.

Tabatha, as the Linux Documentation Project Review Coordinator (at the time) also gave a brief review of this document. Her general advice was used to improve the structure, language and grammar of the document.

Rahul provided a brief review of this document for the Linux Documentation Project. Advice from his brief review was integrated into this document to improve readability and structure, several references were added as recommended by Rahul.

David's criticism of the document (via the TLDP discuss list) were listened to, and attempts to improve the document were made. A number of his criticisms were addressed and improved.

George provided a second language review. His detailed review of the material allowed me to improve the general grammar of the document and some minor errors.

Machtelt provided tips in regard to referencing the correct LDP documents from this guide. As well as general advice on improvements to the guide.

Michael pointed out a number of technical errors in the document after his brief review on behalf of the TLDP during posts to the discussion list.

Use the TAB key and bash will attempt to complete the command for you automatically. You can use it to complete command (tool) names. You can also use it when working with the file-system, when changing directories, copying files et cetera.

There are also other lesser known ways to use automatic command completion (for example completing user names):[1]

Special-characters:

Use the following special characters combined with either ESC-Y or CTRL-X-Y , where Y is some special characters. For example ESC-$ or CTRL-X-$ to complete an environment variable name.

• ~ (tilde) complete a user name

• @ (at sign) complete a machine name

• $ (dollars sign) complete an environment variable name

• ! (exclamation mark) a magic character for completing a command name or a file name. The ! special character has the same function as the TAB key. It works in some other situations; for example when completing man page names.

The alias command will list your current aliases. You can use unalias to remove the alias (to disable it just for one command add a “\” (back-slash) before the command)...

An alias allows one command to be substituted for another. This is used to make a command do something else or to automatically add certain options. This can be either be done during one session using the alias command (see below) or the information can be added to the .bashrc file (found in the users home directory).

Below is an example of what an alias section (within your .bashrc file) might look like:

# my personal aliases
alias cp='cp -vi' #to prompt when copying if you want to overwrite and will tell you where information is going 
alias rm='rm -i' #Prompts you if you really want to remove it.
alias mv='mv -i' #Prompts you if you are going to overwrite something

On any Mandriva GNU/Linux system the global aliases (for all users) are all in /etc/profile.d/alias.sh. The above listed commands already have aliases, as well as several other commonly used commands.

set is one of bash's inbuilt commands, try looking in the bash manual for its many usage options.

Using set with the -x option will make bash print out each command it is going to run before it runs it.

This can be useful to find out what is happening with certain commands such as things being quoted that contain wildcards or special symbols that could cause problems, or complex aliases. Use set +x to turn this back off.

Examples

After using set -x you can run the command:

ls

The output printed before the command runs (for example):

+ ls -F --color=auto 

Which means that the command is really an alias to run ls with the -F and --color=auto options. Use a “\” (backslash) before the command to run it without the alias.

The backslash escape character can be used before a shell command to override any aliases.

For example if rm was made into an alias for rm -i then typing “rm” would actually run rm -i.

However, typing \rm lets the shell ignore the alias and just run rm (its runs exactly what you type), this way it won't confirm if you want to delete things.

	Using rm
	Please note that the alias for the remove command is there for a reason. Using it incorrectly could remove files which you don't want removed. Only use \rm if you know exactly what you are doing (recovering files is not easy, rm does not send things to a recycle bin).

The “\” character can be used before special characters (such as a space or a wildcard), to stop bash from trying to expand them. You can make a directory name with a space in it using a backslash before the space. For example you could type cd My\ Directory\ With\ Spaces which normally wouldn't work.

The “\” character can also be used to stop bash from expanding certain symbols (as an alternative you could use single quotation marks, although you may need to use both).

	The TAB Key
	Please note that using the TAB key (automatic-command-completion) will automatically use escapes for spaces (so you don't have to type them manually).

The “script” command creates a typescript, or "capture log" of a shell session - it writes a copy of your session to a file, including commands you type and their output.

The tilde character is used as an alias to a users home directory.

For example, if your user-name was “fred”, instead of typing cd /home/fred you could simply type cd ~. Or to get to fred's tmp directory (under his home directory) you could type cd ~/tmp.

	Home directory shortcut
	~ (tilde) can also be used as a shortcut to other users home directories, simply type: ~user_name and it will take you to the users home directory. Note that you need to spell the username exactly correct, no wildcards.

This particular set command will turn off the system bell from the command-line (use xset -b for X windows). If you want the bell to stay off pernamently (no audible bell) then you can add this command to your “.bashrc” or “.bash_profile” (just add it to the same one you have your alises in...).

The reset command re-initializes your current terminal. This can be useful when the text from your terminal becomes garbled, simply type “reset” and this will fix your terminal.

Closes your current terminal (with x-terminals) or logs-out. Also try CTRL-D .

Logs out of a terminal, also try CTRL-D .

A little command that repeats anything you type.

Example:

echo “hello world”

Simply displays “ hello world”.

Example:

echo rm -R *

This will output what will be passed to the rm command (and therefore what would be deleted), putting echo before a command renders it harmless (it just expands wildcards so you know what it will do).

Also try using the -e option with echo. This will allow you to use the escape character sequences to format the output of a line. Such as '\t' for tab, '\n' for newline etc.

	Using echo to prevent accidents
	Typing: echo command(s) could save you the trouble of accidentally doing something you didn't expect. Using echo allows you to expand the wildcards to understand what will happen before you actually run the command.

Use the up and down key's to scroll through previously typed commands. Press [Enter] to execute them or use the left and right arrow keys to edit the command first. Also see history (below).

The history command can be used to list Bash's log of the commands you have typed:

This log is called the “history”. To access it type:

history n

This will only list the last n commands. Type “history” (without options) to see the the entire history list.

You can also type !n to execute command number n. Use !! to execute the last command you typed.

!-n will execute the command n times before (in other words !-1 is equivalent to !!).

!string will execute the last command starting with that “string” and !?string? will execute the last command containing the word “string”. For example:

!cd

Will re-run the command that you last typed starting with “cd”.

“ commandName !*” will execute the “commandName” with any arguments you used on your last command. This maybe useful if you make a spelling mistake, for example. If you typed:

emasc /home/fred/mywork.java /tmp/testme.java

In an attempt to execute emacs on the above two files this will obviously fail. So what you can do is type:

emacs !*

This will execute emacs with the arguments that you last typed on the command-line. In other words this is equivalent to typing:

emacs /home/fred/mywork.java /tmp/testme.java

Use the CTRL-R key to perform a “reverse-i-search”. For example, if you wanted to use the command you used the last time you used snort, you would type:

CTRL-R then type “snort”.

What you will see in the console window is:

(reverse-i-search)`':

After you have typed what you are looking for, use the CTRL-R key combination to scroll backward through the history.

Use CTRL-R repeatedly to find every reference to the string you've entered. Once you've found the command you're looking for, use [Enter] to execute it.

Alternatively, using the right or left arrow keys will place the command on an actual command-line so you can edit it.

the “end-of-file” (EOF) key combination can be used to quickly log out of any terminal. CTRL-D is also used in programs such as “at” to signal that you have finished typing your commands (the EOF command).

key combination is used to stop a process. It can be used to put something in the background temporarily.

For example, if you were editing a file with vim or emacs just press CTRL-Z to regain control of the terminal do what you want and then type fg to bring it back.

For further information please see Section 9.3.

	If fg doesn't work
	If fg doesn't work you may need to type jobs and then fg job_name or fg job_number

These key combinations are used for going to the start and end of the line on the command line. Use CTRL-A to jump to the start of the line, and CTRL-E to jump to the end of the line.

This key combination can be used to cut or delete what is currently in front of the cursor.

This key combination can be used to paste the last thing you deleted (using CTRL-K or CTRL-W ).

This key combination can be used to cut or delete the entire line that has being typed.

is a great program that allows you to switch between multiple virtual terminals on the one physical terminal that you are using. Its a command-line based window manager, clearly this isn't that useful if you do have virtual terminals, but its amazingly useful when you log into machines remotely, using ssh and similar, see Section 13.3. It works on key-combinations, you type

screen

On the command-line to begin. Now you start with one virtual terminal by default, but using the key combination CTRL-A and then hitting "C" you can create another virtual terminal to use.

Use CTRL-N to go to the next virtual terminal and CTRL-P to go to the previous virtual terminal. Also try hitting CTRL-A to go backwards and forwards between two particular terminals.

screen also has various other abilities that you can test out. The documentation and guides are well written so please feel free to read the manual page or try searching the internet.

Standard output is the output from the program printed to the screen, not including error output (see below).

Standard input is the input from the user. Normally the keyboard is used as the standard input device in a UNIX system.

Standard error is error output from programs. This output is also sent to the screen and will normally be seen mixed in with standard output. The difference between standard output and standard error is that standard error is unbuffered (it appears immediately on the screen) and standard error is only printed when something goes wrong (it will give you details of what went wrong).

The greater than symbol is used to send information somewhere (for example a text file)

Example:

cat file1 file2 > file1_and_2.txt

This will concatenate the files together into one big file named “file1_and_2.txt”. Note that this will overwrite any existing file.

The less than symbol will insert information from somewhere (a text file) as if you typed it yourself. Often used with commands that are designed to get information from standard input only.

For example (using tr):

tr '[A-Z]' '[a-z]' < fileName.txt > fileNameNew.txt

The example above would insert the contents of “fileName.txt” into the input of tr and output the results to “fileNameNew.txt”.

The >> symbol appends (adds) information to the end of a file or creates one if the file doesn't exist.

The << symbol is sometimes used with commands that use standard input to take information. You simply type << word (where word can be any string) at the end of the command. However its main use is in shell scripting.

The command takes your input until you type “word”, which causes the command to terminate and process the input.

Using << is similar to using CTRL-D (EOF key), except it uses a string to perform the end-of-file function. This design allows it to be used in shell scripts.

For example type "cat" (with no options...) and it will work on standard input.

To stop entering standard input you would normally hit CTRL-D .

As an alternative you can type "cat << FINISHED", then type what you want.

When you are finished, instead of hitting CTRL-D you could type "FINISHED" and it will end (the word FINISHED will not be recorded).

Redirects error output. For example, to redirect the error output to /dev/null, so you do not see it, simply append this to the end of another command...

For example:

make some_file 2> /dev/null

This will run make on a file and send all error output to /dev/null

The “pipe” command allows the output of one command to be sent to the input of another.

For example:

cat file1.txt file2.txt | less

Concatenates the files together, then runs less on them. If you are only going to look at a single file, you would simply use less on the file...

Sends output of a program to a file and to standard output. Think of it as a T intersection...it goes two ways.

For example:

ls /home/user | tee my_directories.txt

Lists the files (displays the output on the screen) and sends the output to a file: “my_directories.txt”.

Redirects standard output and error output to a specific location.

For example:

make &> /dev/null

Sends both error output and standard output to /dev/null so you won't see anything...

Simply type:

command_1 `command_2 -options`

This will execute “command_2” and it's output will become the input to “command_1”.

	Backquote key
	The back-quote key is usually located at the same place as the tilde, above the [Tab] key.

Simply type:

command_1 $(command_2)

This will execute “command_2” and it's output will become the input to “command_1”.

You can of course use pipes to do the same thing, if you don't know what a pipe is, please see Section 6.2. For example instead of doing:

less $cat file1.txt file2.txt

You could do:

cat file1.txt file2.txt | less

And end up with exactly the same result, it's up to you which way you find easier.

To do this you would type:

command1 && command2

command2 will be executed if command1 successfully completes (if command1 fails command2 won't be run). This is called a logical AND.

To do this you would type:

command1 || command2

command2 will be executed if command1 does not successfully complete (if command1 is successful command2 won't be run). This is called a logical OR.

To execute commands sequentially regardless of the success/failure of the previous you simply type:

command1; command2

command2 will execute once command1 has completed.

	More than two commands
	You can continue to use ';' (semicolon) characters to do more and more commands on the one line.

Change directory. Use “ cd ..” to go up one directory.

One dot '.' represents the current directory while two dots '..' represent the parent directory.

“ cd -” will return you to the previous directory (a bit like an “undo”).

You can also use cd absolute path or cd relative path (see below):

For example to get to /boot/grub you would type:

cd /boot/grub

This is an absolute path because you start at the top of the hierarchy and go downwards from there (it doesn't matter where in the filesystem you were when you typed the command).

Please note that there is no / using the above cd command. Using a / would cause this to be an absolute path, working from the top of the hierarchy downward.

List files and directories. Typing “ls” will list files and directories, but will not list hidden files or directories that start with a leading full stop “.”.

Example options:

• ls -l --- long style, this lists permissions, file size, modification date, ownership.

• ls -a --- this means "show all", this shows hidden files, by default any file or directory starting with a '.' will not be shown.

• ls -d --- list directory entires rather than contents (see example below)

• ls -F --- append symbols to particular files, such as * (asterisk) for executable files.

• ls -S --- sort the output of the command in decending order sorted by size.

• ls -R --- (recursive) to list everything in the directories below as well as the current directory.

Command syntax, either:

ls -options

This simply lists everything in the current directory, the options are not required (options such as -l, -a et cetera).

ls -options string

This lists files using a certain string. The string can contain standard wildcards to list multiple files, to learn more about standard wildcards please read Section 20.4.1

You can use ls -d to show directories that match an exact string, or use standard wildcards. Type “ ls -d */” to list all subdirectories of the current directory. Depending on the setup of your aliases (see Chapter 4) you may simply be able to type lsd as the equivalent to ls -d */.

Examples for ls -d:

ls -d */

Lists all subdirectories of current directory.

ls -d string*

Lists directories that start with "string".

ls -d /usr/*/*/doc

Lists all directories that are two levels below the /usr/ directory and have a directory called “doc”, this trick can come in quite handy sometimes.

	You can also use
	Depending on how your aliases (see Chapter 4) are setup you can also use l, la (list all) and ll (list long) to perform the above commands

Print working directory. Print the absolute (complete) path to the directory the user is currently in.

Command syntax:

pwd

This will tell you the full path to the directory you are in, for example it may output “/usr/local/bin” if you are currently in that directory.

Outputs an ASCII text tree/graph starting at a given directory (by default the current directory). This command recursively lists all files and all directories.

In other words, it will list files within the directories below the current one, as well as all files in the current directory.

tree has a large number of options, refer to the manual page for details.

Command syntax:

tree

or

tree -option(s) /optional/directory/to/list

Make a directory. Use mkdir -p to create subdirectories automatically.

	Directories are Folders
	Directories are sometimes called folders in other operating systems (such as Microsoft Windows)

Examples:

mkdir -p /home/matt/work/maths

This would create the directories “work” and “maths” under matt's home directory (if matt's home directory didn't exist it would create that too).

mkdir foo

This would create a directory in the current path named “foo”.

Remove/delete a file(s) or directories(s). You can use standard wildcards with this command Section 20.4.1.

Command syntax:

rm -options file_or_folder

You can of course use standard wildcards to delete multiple files or multiple directories and files.

Use the -R or -r option to remove recursively, this removes everything within subdirectories. Also try the -f option to force removal (useful when you don't want to be prompted).

	Disabling Aliases (per execution)
	On some systems such as Mandrake an alias will send rm to rm -i (prompting you for every file you wish to delete). To override this use: \rm -R directory (using the \ disables the alias for this run only)

Remove an empty directory. If you want to remove a directory with files in it type “ rm -R directory”, read above for information on rm -R

Command syntax:

rmdir directory

This will only remove directory if it's empty otherwise it will exit with an error message.

Move a file or a directory to a new location or rename a file/directory.

Rename example:

mv filename1 filename2

Renames filename1 to filename2.

To move a file or directory, simply type:

mv original_file_or_folder new_location

Note that this command can use standard wildcards Section 20.4.1 to move files (not for renaming).

	Move and rename
	Note that you can also move and rename a file in a single command. The difference is with the destination (right hand side) you change the filename to the new name of the file. For example typing: mv /etc/configuration.txt /home/joe/backupconfig This would move the file "configuration.txt" to /home/joe/ and rename it "backupconfig"

Copy a file. Has a number of useful options, such as -R (or -r) which recursively copies directories and subdirectories.

Command syntax:

cp -options file_or_files new_location

Examples:

cp file1 file2

Simply copy file1 to file2 (in the same directory).

cp /tmp/file1 ~/file2 /mnt/win_c

Where the last option is the directory to be copied to. The above example copies two files from different areas of the file system to /mnt/win_c

cp -R directory_and_or_files new_location

This command will copy directories (and all subdirectories) and/or files to new_location

Note that this command can use standard wildcards Section 20.4.1 to copy multiple files.

You may also like to try the “-u” when moving large directories around, this copies only if the source file is newer than the destination to where you are copying to, or if the destination file does not exist at all.

Create a link to a file. There are two types of links:

Securely remove a file by overwriting it first. Prevents the data from being recovered by software (and even by most hardware), please be very careful when using shred as you may never be able to retrieve the data you have run the application on.

For example:

shred -n 2 -z -v /dev/hda1

“What this tells shred, is to overwrite the partition 2 times with random data (- n 2) then finish it up by writing over it with zeroes (-z) and show you its progress (-v). Of course, change /dev/hda1 to the correct partition . Each pass can take some time, which is why I set it to only do 2 random passes instead of the default 25. You can adjust this number, of course, to your particular level of paranoia and the amount of time you have.

Since shred writes on such a low-level, it doesn't actually matter what kind of filesystem is on the partition--everything will be unrecoverable. Once shred is finished, you can shutdown the machine and sell or throw away the drive with peace of mind.

...However, even shre dding devices is not always completely reliable. For example, most disks map out bad sectors invisibly to the application; if the bad sectors contain sensitive data, `shred' won't be able to destroy it. [ shred info page ].”[2]

	Shredding files doesn't work with all filesystems
	Please note that as mentioned in the shred manual page (please see the manual and preferably info pages for more information). shred does not work correctly on log-structured or journaled filesystems, such as JFS, ReiserFS, XFS, Ext3 and many other modern filesystems

Alternatives to using shred

shred has its disadvantages when run on a filesystem. First of all since it has to be installed you cannot run shred on your operating systems filesystem, you also cannot use shred on a windows machine easily since you cannot install shred on this machine. You may like to try alternatives such as the DBAN project that create self-booting floppy disks that can completely erase a machines hard disk.

You may also like to see how chattr can assist you in shredding files once they are removed (it has similar problems to shred, only ext2 and ext3 style filesystems...), please see Section 14.2.

Displays information about file size. Use du filename to display the size of a particular file. If you use it on directories it will display the information on the size of the files in the directory and each subdirectory.

Options for du (use du -option(s)):

• -c -- this will make du print a grand total after all arguments have being processed.

• -s -- summarises for each argument (prints the total).

• -h -- prints things in “ human readable” mode; for example printing 1M (megabyte) rather than 1,024,000 (bytes).

Using the -hs options on a directory will display the total size of the directory and all subdirectories.

Command syntax:

du -options file_directory_or_files

Example:

du -hs *

This command will list the size of all files in the current directory and it will list the size of subdirectories, it will list things in human-readable sizes using 1024 Kb is a Megabyte, M for megabyte, K for kilobyte etc.

Attempts to find out what type of file it is, for example it may say it's: binary, an image file (well it will say jpeg, bmp et cetera), ASCII text, C header file and many other kinds of files, it's a very useful utility.

Command syntax:

file file_name

Tells you detailed information about a file, including inode number creation/access date. Also has many advanced options and uses.

For simple use type:

stat file

Copies data on a very low level and can be used to create copies of disks Section 20.3 and many other things (for example CD image files).

dd can also perform conversions on files and vary the block size used when writing the file.

Command syntax, note the block size and count are optional and you can use files instead of devices...

	Please note
	dd is an advanced and difficult to use command. Its also very powerful, so be careful what you do with it

Command syntax:

dd if=/dev/xxx of=/dev/xxx bs=xxxx count=x 

	Warning
	The command dd is used to work on a very low level. It can be used to overwrite important information such as your master-boot record or various important sections of your hard-disk. Please be careful when using it (especially when working with devices instead of files).

This command is used to create empty files, simply do touch file_name. It is also used to update the timestamps on files.

touch can be used to change the time and/or date of a file:

touch -t 05070915 my_report.txt[3]

This command would change the timestamp on my_report.txt so that it would look like you created it at 9:15. The first four digits stand for May 7th (0507), in MM-DD (American style), and the last four (0915) the time, 9:15 in the morning.

Instead of using plain numbers to change the time, you can use options similar to that of the date tool. For example:

touch -d '5 May 2000' some_file.txt

You can also use --date= instead of -d. Also have a look at the date command under Section 8.1 for examples on using -d and --date= (the syntax for the date part is exactly the same when using -d or --date).

Splits files into several smaller files.

Use the -b xx option to split into xx bytes, also try -k for kilobytes, and -m for megabytes. You can use it to split text files and any other files... you can use cat to re-combine the files.

This may be useful if you have to transfer something to floppy disks or you wish to divide text files into certain sizes.

Command syntax:

split -options file

This will split the input file into 1000 lines of input each (thats the default...), and output (using the above example), with the input name file, “fileaa” (1st part of file), “fileab” (2nd part of file), “fileac” (3rd part of file) etc. until the there is no more of the file left to split.

mmv is a mass move/copy/renaming tool that uses standard wildcards to perform its functions.

mmv's manual page is quite difficult to understand, I have only a limited understanding of this tool. However mmv supports some standard wildcards.

According to the manual the “;” wildcard is useful for matching files at any depth in the directory tree (ie it will go below the current directory, recursively).

An example of how to use mmv is shown below:

mmv \*.JPG \#1.jpg 

The first pattern matches anything with a “.JPG” and renames each file (the “#1” matches the first wildcard) to “.jpg”.

Each time you use a \(wildcard) you can use a #x to get that wildcard. Where x is a positive number starting at 1.

	mmv Homepage
	You can find mmv on the web here. Also be aware that certain options used with mmv are also applicable to other tools in the suite, these include mcp (mass copy), mad (mass append contents of source file to target name), mln (mass link to a source file).

	Tip:
	A Java alternative to mmv which runs on both GNU/Linux and Windows is available, Esomaniac

rename is a perl script which can be used to mass rename files according to a regular expression.

An example for renaming all “.JPG” files to “.jpg” is:

rename 's/\.JPG$/.jpg/' *.JPG 

	Finding rename
	You can get rename from various places. I would recommend trying CPAN Search Site, I found the script here Rename Script Version 1.4

Bash scripting is one way to rename files. You can develop a set of instructions (a script) to rename files. Scripts are useful if you don't have mmv or rename...

One way to this is shown below:

for i in *.JPG; 
do mv $i `basename $i JPG`jpg; 
done 

Note that the above script came from a usenet post. Unfortunately I do not know the author's name.

The first line says find everything with the “.JPG” extension (capitals only, because the UNIX system is case sensitive).

The second line uses basename (type man basename for more details) with the '$i' argument. The '$i' is a string containing the name of the file that matches. The next portion of the line removes the JPG extension from the end and adds the jpg extention to each file. The command mv is run on the output.

An alternative is:

for i in *.JPG; 
do mv $i ${i%%.JPG}.jpg; 
done

The above script renames files using a built-in bash function. For more information on bash scripting you may like to see the advanced bash scripting guide, authored by Mendel Cooper.

Tells you the date (and the time) and is also used to set the date/time.

To set the date, type date MM:DD:YYYY (American style date) where MM is month, DD is the number of days within the month and YYYY is the year.

For example to set the date to the 1st January 2000 you would type:

date 01:01:2000

To set the time (where the -s option is to set a new time), type:

date -s hh:mm:ss

Another useful option you can use is --date=“string” (or -d “string”) option to display a date from x days ago or in x days (or x weeks, months, years et cetera). See the examples below.

Examples:

date --date="3 months 1 day ago"

Will print the date 3 months and 1 day ago from the current date. Note that --date=”x month x day ago” and -d “x month x day ago” are equivalent.

date -d "3 days"

The above command will print the date 3 days in the future from now.

Typing cal will give you the calendar of the present month on your screen, in the nice standard calendar format. There are various options to customise the calendar, refer to the info/man page.

Example:

cal -y year

Will display a calendar for a specific year, simply use cal -y to print the calendar for the current year.

cal 2 2004

This will display the calendar for February 2004

You can look through the information in the relevant area of the proc filesystem, under the directory of either /proc/ide/ or /proc/ide?/hd? where the first question mark is a number and the second is a letter (starting with 'a').

For example:

cd /proc/ide0/hda

Under this directory there will be various information on the hard drive or cdrom connected.

Using fdisk with the -l option will output information on any hard drives connected to the system and information on their partitions (for example, the type of partition).

Information relating to using fdisk to partition hard disks can be found in your distributions documentation, the fdisk manual page or online.

	Root Access Required
	This command needs root access to work

Mount a device. Attach the device to the file-system hierarchy (the tree ( / )). This needs to be done so you can access the drive (see below, Section 9.1 for an example).

'Unmount' a device. The command umount (no 'n') unmount's a device. It removes it from the file-system hierarchy (the tree ( / )). This needs to be done before you remove a floppy/CDROM or any other removable device (see below, Section 9.1 for an example).

Where “win” would be the place you want it mounted and “wincomp” is the IP address or name of your windows computer.

	Please note
	Using ping/smbmount/ssh or other UNIX system programs with a computer name rather than IP address will only work if you have the computer listed in your /etc/hosts file. Here is an example: 192.168.1.100 new This line says that their is a computer called “new” with IP address 192.168.1.100. Now that it exists in the /etc/hosts file I don't have to type the IP address anymore, just the name “new”.

smbmount is a tool from the samba package, it can mount a remote windows file-system onto your current computer.

Un-mounting uses the same syntax as 'umount', as listed above, or you may like to use:

smbumount /mountpoint

Here are some more examples of how to mount a file-system:

mount -t ext2 /dev/fd0 /mnt/floppy 
mount -t iso9660 /dev/hdb /mnt/cdrom 
mount -t iso /tmp/image_file /mnt/iso_file/ -o loop