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NAME | DESCRIPTION | NOTES | SEE ALSO | COLOPHON |
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intro(1) General Commands Manual intro(1)
intro - introduction to user commands
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.
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.
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)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 intro(1)
Pages that refer to this page: sortman(1), intro(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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