Skip to main content Link Search Menu Expand Document (external link)
CIS Tutorials

Unix Tutorial Two

Step 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 cs1 directory.

First, cd to your cs1 directory.

cd ~/cs1

Then at the UNIX prompt, type:

cp /usr/share/dict/words .

(Note: Don’t forget the dot “.” at the end, which means the current directory.)

The above command copy the file words to the current directory, keeping the name the same.

Exercise:

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

Step 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 words to your backup directory.

First, change directories to your cs1 directory (can you remember how?). Then, inside the cs1 directory, type:

% mv words backups

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

Step 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 words file then delete it.

Inside your cs1 directory, type:

  cp words words.backup  
  ls #to check if it has created the file 
  rm words.backup  
  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). Try to remove the backups directory. You will not be able to since UNIX will not let you remove a non-empty directory.

Exercise:

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

Step 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 words

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 words

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.

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

First clear the screen then type:

  head words

Then type:

  head -5 words

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 words

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

Step 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 words for the word police, type:

  less words

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

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 bail words

As you can see, grep has printed out each line containg the word bail.

Or has it????

Try typing:

% grep Bail words

The grep command is “case sensitive”; it distinguishes between Bail and bail.

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

% grep -i bail words

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 'file sharing' words

Some of the other options of grep are:

  • v display those lines that do NOT match
  • n precede each maching 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 police or Police is:

 grep -ivc police words

wc (word count)

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

 wc -w words

To find out how many lines the file has, type:

 wc -l words

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

M.Stonebank@surrey.ac.uk
© 9th October 2000
Adapted by Xiaolan Zhang based on http://www.math.montana.edu/help/software/unixtut/unix1.html