Unix tutorial Two 1 Copying Files




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UNIX Tutorial Two

2.1 Copying Files

cp (copy)


cp file1 file2 is the command which makes a copy of file1 in the current working directory and calls it file2

What we are going to do now, is to take a file stored in an open access area of the file system, and use the cp command to copy it to your public_html directory.

First create a directory named temp in your home folder, then change directories into it.

% mkdir temp


% cd temp

Then at the UNIX prompt, type,

% cp /usr/local/etc/apache2/httpd.conf .

(Note: Don't forget the dot (.) at the end. Remember, in UNIX, the dot means the current directory.)

The above command means copy the file httpd.conf to the current directory, keeping the name the same.

(Note: The directory /usr/local/etc/apache2/ is the area where Apache stores all of its configuration files.

 

Exercise 2a


Create a backup of your httpd.conf file by copying it to a file called httpd.conf.bak

2.2 Moving files

mv (move)


mv file1 file2 moves (or renames) file1 to file2

To move a file from one place to another, use the mv command. This has the effect of moving rather than copying the file, so you end up with only one file rather than two.

It can also be used to rename a file, by moving the file to the same directory, but giving it a different name.

We are now going to move the file httpd.conf.bak out of the temp directory.

First, change directories to your temp directory (can you remember how?). Then, inside the temp directory, type

% mv httpd.conf.bak ..

Type ls and ls .. to see if it has worked.

2.3 Removing files and directories

rm (remove), rmdir (remove directory)


To delete (remove) a file, use the rm command. As an example, we are going to create a copy of the httpd.conf file then delete it.

Inside your tempdirectory, type

% cp httpd.conf tempfile.txt
% ls (to check if it has created the file)
% rm tempfile.txt
% ls (to check if it has deleted the file)

You can use the rmdir command to remove a directory (make sure it is empty first).

 

Exercise 2b


Create a directory called tempstuff using mkdir , then remove it using the rmdir command.

2.4 Displaying the contents of a file on the screen

clear (clear screen)


Before you start the next section, you may like to clear the terminal window of the previous commands so the output of the following commands can be clearly understood.

At the prompt, type

% clear

This will clear all text and leave you with the % prompt at the top of the window.

 

cat (concatenate)


The command cat can be used to display the contents of a file on the screen. Type:

% cat httpd.conf

As you can see, the file is longer than than the size of the window, so it scrolls past making it unreadable.

 

less


The command less writes the contents of a file onto the screen a page at a time. Type

% less httpd.conf

Press the [space-bar] if you want to see another page, type [q] if you want to quit reading. As you can see, less is used in preference to cat for long files.

You can also use the command more to do the same thing. On most modern Unixes more is just a symbolic link (shortcut) to less.

 

head


The head command writes the first ten lines of a file to the screen.

First clear the screen then type

% head httpd.conf

Then type

% head -5 httpd.conf

What difference did the -5 do to the head command?

 

tail


The tail command writes the last ten lines of a file to the screen.

Clear the screen and type

% tail httpd.conf

How can you view the last 15 lines of the file?

 

2.5 Searching the contents of a file

Simple searching using less


Using less, you can search though a text file for a keyword (pattern). For example, to search through httpd.conf for the word 'science', type

% less httpd.conf

then, still in less (i.e. don't press [q] to quit), type a forward slash [/] followed by the word to search

/DirectoryIndex

As you can see, less finds and highlights the keyword. Type [n] to search for the next occurrence of the word.

 

grep


grep is one of many standard UNIX utilities. It searches files for specified words or patterns. First clear the screen, then type

% grep VirtualHost httpd.conf

As you can see, grep has printed out each line containing the word VirtualHost.

The grep command is case sensitive.

To ignore upper/lower case distinctions, use the -i option, i.e. type

% grep -i virtualhost httpd.conf

To search for a phrase or pattern, you must enclose it in single quotes (the apostrophe symbol). For example to search for spinning top, type

% grep -i 'maintain multiple' httpd.conf

Some of the other options of grep are:

-v display those lines that do NOT match


-n precede each matching line with the line number
-c print only the total count of matched lines

Try some of them and see the different results. Don't forget, you can use more than one option at a time, for example, the number of lines without the words VirtualHost or virtualhost is

% grep -ivc virtualhost httpd.conf

 

wc (word count)


A handy little utility is the wc command, short for word count. To do a word count on httpd.conf, type

% wc -w httpd.conf

To find out how many lines the file has, type

% wc -l httpd.conf


Summary


cp file1 file2

copy file1 and call it file2

mv file1 file2

move or rename file1 to file2

rm file

remove a file

rmdir directory

remove a directory

cat file

display a file

more file

display a file a page at a time

head file

display the first few lines of a file

tail file

display the last few lines of a file

grep 'keyword' file

search a file for keywords

wc file

count number of lines/words/characters in file

 


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