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RedHat 9 (Linux i386) - man page for intro (redhat section 1)

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

NAME
       intro - Introduction to user commands

DESCRIPTION
       Linux is a flavour 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 tradi-
       tional 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 inter-
       preter) 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. Everybody has her own favourite one.   The  stan-
       dard 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 user name, machine name, cur-
       rent directory, time, etc.  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 givs a cal-
       endar).

       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 concatenated 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 wastepa-
       per 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.

   Path names and the current directory
       Files  live in a large tree, the file hierarchy.  Each has a path name describing the path
       from the root of the tree (which is called /) to the file. For example, such a  full  path
       name  might be /home/aeb/tel.  Always using full path names would be inconvenient, and the
       name of a file in the current directory may be abbreviated by only giving the last  compo-
       nent.  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-consum-
       ing, and it may be better to use locate(1).

   Disks and Filesystems
       The command mount will attach the filesystem found on some disk (or floppy,  or	CDROM  or
       so)  to	the  big filesystem 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 talk-
       ing 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  pro-
       cesses can often be killed by typing Control-C.

   Getting information
       There are thousands of commands, each with many options.  Traditionally commands are docu-
       mented 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 custumary to refer to man pages by giving the name and section num-
       ber, 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 introduc-
       tion 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.

Linux					    2002-08-06					 INTRO(1)


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