Manpage of INTRO

INTRO

Section: Linux User's Manual (1)
Updated: 2015-07-23
Index
 

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 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 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 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 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: aebPassword: ********$ dateTue 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

$ lsbin  tel
$ ls -ltotal 2
drwxrwxr-x   2 aeb       1024 Aug  6 23:51 bin
-rw-rw-r--   1 aeb         37 Aug  6 23:52 tel
$ cat telmaja    0501-1136285
peter   0136-7399214
$ cp tel tel2$ ls -ltotal 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 -ltotal 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 tel2maja    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 lslists the contents of the current directory---it tells you what files you have. With a -loption 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 chownand chmod.

The command catwill 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 difflists 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 pathnamedescribing 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/telcan be abbreviated to telwhen the current directory is /home/aeb.

The command pwdprints the current directory.

The command cdchanges the current directory.

Try alternatively cdand pwdcommands and explore cdusage: "cd", "cd .", "cd ..", "cd /" and "cd ~".  

Directories

The command mkdirmakes a new directory.

The command rmdirremoves 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 telstarting 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 mountwill attach the filesystem found on some disk (or floppy, or CDROM or so) to the big filesystem hierarchy. And umountdetaches it again. The command dfwill 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 pswill show you which processes are active and what numbers these processes have. The command killallows 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 mansends 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/enand use a browser if you find HTML files there.  

SEE ALSO

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)


 

Index

NAME
DESCRIPTION
NOTES
Login
The shell
Pathnames and the current directory
Directories
Disks and filesystems
Processes
Getting information
SEE ALSO

This document was created by man2html, using the manual pages.
Time: 22:27:40 GMT, June 20, 2016