Basic Commands

• A UNIX command is typed in at the command-line prompt. It consists of 3 parts:
  1. the command. This always comes first.
  2. flags. A flag has a dash in it (i.e. -l). Usually flags are optional and allow you to give specific instructions to the command you are running.
  3. arguments. Some commands need to know a particular file to manipulate, which is specified as a command-line argument.
• For instance:

     cat abc
  

  will show the contents of the file called abc.
• This command:

     cat -v abc
  

  uses the -v flag (for verbose mode) to also show where the tabs are.
• Here are a list of some basic commands and what they do. We will be using more than these. Which ones do not exist in your flavor of LINUX?
  

  Command	Description
  basename pathname	show the final part (filename or directory) of the pathname. Can take an additional argument, which is a suffix to be stripped. For instance running the command below will print resume: basename $HOME/resume.doc .doc Try: dirname /abc/def/123
  cd directory	change working directory. After the command, type in the new directory you want to go to. It will make that directory your current one.
  cal	show a calendar for the current month. You can also specify a year and see the calendar for the whole year. (i.e. cal 2001)
  cat file_name	print the contents of a file to the screen. It is your responsibility to make sure to only cat a text file.
  chmod	change the mode of a file to allow different permissions.
  cp original_file new_file	copy the original file to a file named new_file. If the new file already exists, it will be overwritten.
  cpio	copy or backup files. Similar to zip.
  date	display the current date and time. You can optionally specify formatting options. For instance, running the command below on a Sunday will print out "Today is Sunday." date '+Today is %A.'
  diff file1 file2	shows the differences between the two files.
  dirname pathname	show the directory pathname containing the specified pathname; it strips off everything after the last slash. Try: dirname /abc/def/123
  echo arguments	print the arguments to the screen.
  exit	log off the system.
  file file_name	display what type of file it is. UNIX does not pay attention to extensions. So, just because a file is named file.txt does not mean that it is a text file.
  find	search for files.
  grep	search files for a particular regular expression (more on that later).
  head	shows the first few lines in a file.
  ls	list the contents of a directory. The -l flag will give you a long listing that includes information about each file.
  man command	print the online manual page for the command. Press space to see the next page. Enter q to quit.
  mkdir directory_name	make a new directory (folder).
  more	show the contents of a file, one page at a time. Press space to see the next page. Enter q to quit.
  mv original_file new_file	move the original file to a file named new_file. If the new file already exists, it will be overwritten.
  od	octal dump. shows the contents of a file as octal characters. Used to examine non-text files.
  passwd	change your password.
  ps	process status. This lists information about running processes.
  pwd	print working directory. It will tell you what directory (folder) you are in.
  rm file_name	remove the file. There is no undo, so be careful!
  rmdir directory_name	remove the directory. The directory must be empty.
  sort	sorts its input alphabetically.
  stty	set terminal options.
  tar	copy or backup files (stands for tape archive). Similar to zip.
  tail	shows the last few lines in a file.
  wc	word count. Counts characters, words, and lines in a file.
  who	display all the users currently logged into the machine.