A copy from UNIX Tutorial for Beginners with modified paths
Please use this terminal emulator when doing the exercises!
UNIX Tutorial Two
2.1 Copying Files
NOTE: Terminals can have many different appearances, which can be confusing in the beginning. The thing all the appearances have in common is that they have 'strange character' as indicator of the line where you type stuff. In this exercises they use the percent character, %, and in the terminal emulator they have chosen the brackets character, # . Most commonly used is the dollar character, $ .
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 unixstuff directory.
First, cd to your unixstuff directory.
% cd ~/unixstuff
Then at the UNIX prompt, type,
% cp /root/dos/asm-1.9/readme.txt .
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 readme.txt to the current directory, keeping the name the same.
Exercise 2a
Create a backup of your readme.txt file by copying it to a file called readme.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 readme.bak to your backup directory.
First, change directories to your unixstuff directory (can you remember how?). Then, inside the unixstuff directory, type
% mv readme.bak backups/.
Type ls and ls backups 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 readme.txt file then delete it.
Inside your unixstuff directory, type
% cp readme.txt tempfile.txt
% ls
% rm tempfile.txt
% ls
You can use the rmdir command to remove a directory (make sure it is empty first). Try to remove the backups directory. You will not be able to since UNIX will not let you remove a non-empty directory.
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 readme.txt
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 readme.txt
Press the [space-bar] if you want to see another page, and type [q] if you want to quit reading. As you can see, less is used in preference to cat for long files.
head
The head command writes the first ten lines of a file to the screen.
First clear the screen then type
% head readme.txt
Then type
% head -5 readme.txt
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 readme.txt
Q. 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 readme.txt for the word 'data', type
% less readme.txt
then, still in less, type a forward slash [/] followed by the word to search
/data
As you can see, less finds the first row that contains the keyword, and scrolls down so it becomes the top row in the window.. Type [n] to search for the next occurrence of the word.
grep (don't ask why it is called grep)
grep is one of many standard UNIX utilities. It searches files for specified words or patterns. First clear the screen, then type
% grep data readme.txt
As you can see, grep has printed out each line containg the word data.
Or has it ????
Try typing
% grep Data readme.txt
The grep command is case sensitive; it distinguishes between Data and data.
To ignore upper/lower case distinctions, use the -i option, i.e. type
% grep -i data readme.txt
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 'goes to the' readme.txt
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 data or Data is
% grep -ivc data readme.txt
wc (word count)
A handy little utility is the wc command, short for word count. To do a word count on readme.txt, type
% wc -w readme.txt
To find out how many lines the file has, type
% wc -l readme.txt
Summary
| Command | Meaning |
|---|---|
| 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 |
| less 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 |
M.Stonebank@surrey.ac.uk, © 9th October 2000