# intro

## 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.
    


## NOTES



           Linux is a flavor of UNIX, and user commands under UNIX work
           similarly under Linux (and lots of other UNIX-like systems too,
           like FreeBSD).
    
           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.  This is faster and more
           powerful, but requires finding out what the commands are and how
           to use them.  Below is a bare minimum guide to get you started.
    
       **Login**
           In order to start working, you'll probably first have to open a
           session.  The program login(1) will wait for you to type your
           username and password, and after that, it will start 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 into the _shell_ , the command interpreter.  It is
           not built-in; it is just another program.  You can change your
           shell, and everybody has their own favorite one.  The standard one
           is called _sh_.  See also **ash**(1), bash(1), chsh(1), **csh**(1), dash(1),
           **ksh**(1), **zsh**(1).
    
           A session might look like this:
    
               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
               $
    
           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 directory, 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
           concatenated and sent to "standard output" (see stdout(3)), here
           the terminal screen.)
    
           The command _cp_ (from "copy") will copy a file.
    
           The command _mv_ (from "move"), on the other hand, 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 giving only 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 alternatively _cd_ and _pwd_ commands and explore _cd_ usage: "cd",
           "cd .", "cd ..", "cd /", and "cd ~".
    
       **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 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 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.
    


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