INTRO(1)							Linux User's Manual							  INTRO(1)

NAME

       intro - introduction to user commands

DESCRIPTION

       Section	1 of the manual describes user commands and tools, for example, file manipulation tools, shells, compilers, web browsers, file and
       image viewers and editors, and so on.

       All commands yield a status value on termination.  This value can be tested (e.g., in most shells the variable $?  contains the	status	of
       the  last  executed command) to see whether the command completed successfully.	A zero exit status is conventionally used to indicate suc-
       cess, and a nonzero status means that the command was unsuccessful.  (Details of the exit status can be found in wait(2).)  A nonzero  exit
       status can be in the range 1 to 255, and some commands use different nonzero status values to indicate the reason why the command failed.

NOTES

       Linux  is  a flavor of UNIX, and as a first approximation all user commands under UNIX work precisely the same under Linux (and FreeBSD and
       lots of other UNIX-like systems).

       Under Linux there are GUIs (graphical user interfaces), where you can point and click and drag, and hopefully get work done  without  first
       reading	lots  of  documentation.   The traditional UNIX environment is a CLI (command line interface), where you type commands to tell the
       computer what to do.  That is faster and more powerful, but requires finding out what the commands are.	 Below	a  bare  minimum,  to  get
       started.

   Login
       In  order  to  start  working, you probably first have to login, that is, give your username and password.  See also login(1).  The program
       login now starts a shell (command interpreter) for you.	In case of a graphical login, you get a screen with menus or  icons  and  a  mouse
       click will start a shell in a window.  See also xterm(1).

   The shell
       One types commands to the shell, the command interpreter.  It is not built-in, but is just a program and you can change your shell.  Every-
       body has her own favorite one.  The standard one is called sh.  See also ash(1), bash(1), csh(1), zsh(1), chsh(1).

       A session might go like

	      knuth login: aeb
	      Password: ********
	      % date
	      Tue Aug  6 23:50:44 CEST 2002
	      % cal
		   August 2002
	      Su Mo Tu We Th Fr Sa
			   1  2  3
	       4  5  6	7  8  9 10
	      11 12 13 14 15 16 17
	      18 19 20 21 22 23 24
	      25 26 27 28 29 30 31

	      % ls
	      bin  tel
	      % ls -l
	      total 2
	      drwxrwxr-x   2 aeb       1024 Aug  6 23:51 bin
	      -rw-rw-r--   1 aeb	 37 Aug  6 23:52 tel
	      % cat tel
	      maja    0501-1136285
	      peter   0136-7399214
	      % cp tel tel2
	      % ls -l
	      total 3
	      drwxr-xr-x   2 aeb       1024 Aug  6 23:51 bin
	      -rw-r--r--   1 aeb	 37 Aug  6 23:52 tel
	      -rw-r--r--   1 aeb	 37 Aug  6 23:53 tel2
	      % mv tel tel1
	      % ls -l
	      total 3
	      drwxr-xr-x   2 aeb       1024 Aug  6 23:51 bin
	      -rw-r--r--   1 aeb	 37 Aug  6 23:52 tel1
	      -rw-r--r--   1 aeb	 37 Aug  6 23:53 tel2
	      % diff tel1 tel2
	      % rm tel1
	      % grep maja tel2
	      maja    0501-1136285
	      %
       and here typing Control-D ended the session.  The % here was the command prompt--it is the shell's way of indicating that it is	ready  for
       the  next  command.   The prompt can be customized in lots of ways, and one might include stuff like username, machine name, current direc-
       tory, time, and so on.  An assignment PS1="What next, master? " would change the prompt as indicated.

       We see that there are commands date (that gives date and time), and cal (that gives a calendar).

       The command ls lists the contents of the current directory--it tells you what files you have.  With a -l option it gives  a  long  listing,
       that  includes the owner and size and date of the file, and the permissions people have for reading and/or changing the file.  For example,
       the file "tel" here is 37 bytes long, owned by aeb and the owner can read and write it, others can only read it.  Owner and permissions can
       be changed by the commands chown and chmod.

       The  command  cat  will show the contents of a file.  (The name is from "concatenate and print": all files given as parameters are concate-
       nated and sent to "standard output", here the terminal screen.)

       The command cp (from "copy") will copy a file.  On the other hand, the command mv (from "move") only renames it.

       The command diff lists the differences between two files.  Here there was no output because there were no differences.

       The command rm (from "remove") deletes the file, and be careful! it is gone.  No wastepaper basket or anything.	Deleted means lost.

       The command grep (from "g/re/p") finds occurrences of a string in one or more files.  Here it finds Maja's telephone number.

   Pathnames and the current directory
       Files live in a large tree, the file hierarchy.	Each has a pathname describing the path from the root of the tree (which is called  /)	to
       the  file.  For example, such a full pathname might be /home/aeb/tel.  Always using full pathnames would be inconvenient, and the name of a
       file in the current directory may be abbreviated by only giving the last component.  That is why  "/home/aeb/tel"  can  be  abbreviated	to
       "tel" when the current directory is "/home/aeb".

       The command pwd prints the current directory.

       The command cd changes the current directory.  Try "cd /" and "pwd" and "cd" and "pwd".

   Directories
       The command mkdir makes a new directory.

       The command rmdir removes a directory if it is empty, and complains otherwise.

       The command find (with a rather baroque syntax) will find files with given name or other properties.  For example, "find . -name tel" would
       find the file "tel" starting in the present directory (which is called ".").  And "find / -name tel" would do the same, but starting at the
       root of the tree.  Large searches on a multi-GB disk will be time-consuming, and it may be better to use locate(1).

   Disks and Filesystems
       The  command mount will attach the file system found on some disk (or floppy, or CDROM or so) to the big file system hierarchy.	And umount
       detaches it again.  The command df will tell you how much of your disk is still free.

   Processes
       On a UNIX system many user and system processes run simultaneously.  The one you are talking to runs in the foreground, the others  in  the
       background.  The command ps will show you which processes are active and what numbers these processes have.  The command kill allows you to
       get rid of them.  Without option this is a friendly request: please go away.  And "kill -9" followed by the number of  the  process  is	an
       immediate kill.	Foreground processes can often be killed by typing Control-C.

   Getting information
       There  are thousands of commands, each with many options.  Traditionally commands are documented on man pages, (like this one), so that the
       command "man kill" will document the use of the command "kill" (and "man man" document the command "man").  The program man sends the  text
       through some pager, usually less.  Hit the space bar to get the next page, hit q to quit.

       In documentation it is customary to refer to man pages by giving the name and section number, as in man(1).  Man pages are terse, and allow
       you to find quickly some forgotten detail.  For newcomers an introductory text with more examples and explanations is useful.

       A lot of GNU/FSF software is provided with info files.  Type "info info" for an introduction on the use of the program "info".

       Special topics are often treated in HOWTOs.  Look in /usr/share/doc/howto/en and use a browser if you find HTML files there.

SEE ALSO

       standards(7)

COLOPHON

       This page is part of release 3.44 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2007-11-15								  INTRO(1)