intro(1) — Linux manual page


intro(1)                 General Commands Manual                intro(1)

NAME         top

       intro - introduction to user commands

DESCRIPTION         top

       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         top

       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.

       In order to start working, you probably first have to open a
       session by giving your username and password.  The program
       login(1) 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

   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 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 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

       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

       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

       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 ~".

       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

   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.

       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

   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

SEE ALSO         top

       ash(1), bash(1), chsh(1), csh(1), dash(1), ksh(1), locate(1),
       login(1), man(1), xterm(1), zsh(1), wait(2), stdout(3),
       man-pages(7), standards(7)

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