Simple File Operations

For all the commands below, you can execute them simply by typing them at your prompt. Note that many commands require an argument; that is, if you were creating a new directory, you would have to give the mkdir command the name of the new directory you wished to make.

• pwd: gives your present working directory. It is useful for remembering where you are. If you issued this command when you first log in, it should return a path like the one shown in Section I.3.1.
• ls: lists the files in your current working directory. You can give it options to show file permissions, the last time a file was modified, and other details. The syntax to do this is ls -l. Note that your home directory will contain many files that start with a period (called ``dot-files''). Most of these files are special configuration files. Occasionally you may want to modify them. You can only list these files by giving ls the -a option.
• cd: change directory. Give this command followed by either a relative or absolute path. Say you have a Mail/ subdirectory off of your home directory and you wish to go to it. Here are two commands that do exactly the same thing:

  
  joeblow@laser% cd Mail/ 
  
  joeblow@laser% cd /home/reu/joeblow/Mail/
  

  In the first example you used a relative path while in the second you gave the full (or absolute) path to the directory. Note that you can return to the previous directory by using:
  joeblow@laser% cd ..
  Another note: typing cd by itself will always return you to your home directory.
• mkdir: make a subdirectory. Invoke with the name of the subdirectory you wish to create. To create the subdirectory ``temp'' from your current working directory, simply type
  joeblow@laser% mkdir temp
  Note that you could have also included the trailing slash on the directory (that is, ``temp/'').
• rm: remove a file. Invoke with the name of the file you wish to delete. Use this command with caution - once you delete a file, it is usually irretrievable.
• cp: copy a file. For example to copy file1 to a new file called file2

  
  joeblow@laser% cp file1 file2
  

• mv: move a file. Can also be used to rename a file. Here are two examples:

  
  joeblow@laser% mv file1 Mail/ 
  
  joeblow@laser% mv file1 myfile
  

  In the first example we have moved a file to the subdirectory called ``Mail''. In the second example we have renamed file1 to myfile.

A couple of final caveats about files and commands. Unix is case-sensitive. Almost all Unix commands are lower-case. Another suggestion - be careful when using non-alphanumeric characters. * and ? are used as wild-card characters for instance. Avoid spaces in Unix file names. Instead consider using the underscore character (like my_first_try). Finally, be careful when you copy or move files. Unix will allow you to easily overwrite files with the same names. In the example for cp above, if you already had a file named file2, it would be lost when you copied file1 to file2. You can have Unix warn you about overwriting files if you use the -i option when using cp or mv. This will put you into an interactive mode where you will be prompted if you are about to overwrite a file.