1intro(1)                    General Commands Manual                   intro(1)
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NAME

6       intro - introduction to user commands
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DESCRIPTION

9       Section 1 of the manual describes user commands and tools, for example,
10       file manipulation tools, shells, compilers, web browsers, file and  im‐
11       age viewers and editors, and so on.
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NOTES

14       Linux  is  a flavor of UNIX, and as a first approximation all user com‐
15       mands under UNIX work precisely the same under Linux (and  FreeBSD  and
16       lots of other UNIX-like systems).
17
18       Under  Linux, there are GUIs (graphical user interfaces), where you can
19       point and click and drag, and hopefully get  work  done  without  first
20       reading  lots  of documentation.  The traditional UNIX environment is a
21       CLI (command line interface), where you type commands to tell the  com‐
22       puter what to do.  That is faster and more powerful, but requires find‐
23       ing out what the commands are.  Below a bare minimum, to get started.
24
25   Login
26       In order to start working, you probably first have to open a session by
27       giving  your  username and password.  The program login(1) now starts a
28       shell (command interpreter) for you.  In case of a graphical login, you
29       get  a  screen with menus or icons and a mouse click will start a shell
30       in a window.  See also xterm(1).
31
32   The shell
33       One types commands to the shell, the command interpreter.   It  is  not
34       built-in,  but is just a program and you can change your shell.  Every‐
35       body has their own favorite one.  The standard one is called  sh.   See
36       also ash(1), bash(1), chsh(1), csh(1), dash(1), ksh(1), zsh(1).
37
38       A session might go like:
39
40           knuth login: aeb
41           Password: ********
42           $ date
43           Tue Aug  6 23:50:44 CEST 2002
44           $ cal
45                August 2002
46           Su Mo Tu We Th Fr Sa
47                        1  2  3
48            4  5  6  7  8  9 10
49           11 12 13 14 15 16 17
50           18 19 20 21 22 23 24
51           25 26 27 28 29 30 31
52
53           $ ls
54           bin  tel
55           $ ls -l
56           total 2
57           drwxrwxr-x   2 aeb       1024 Aug  6 23:51 bin
58           -rw-rw-r--   1 aeb         37 Aug  6 23:52 tel
59           $ cat tel
60           maja    0501-1136285
61           peter   0136-7399214
62           $ cp tel tel2
63           $ ls -l
64           total 3
65           drwxr-xr-x   2 aeb       1024 Aug  6 23:51 bin
66           -rw-r--r--   1 aeb         37 Aug  6 23:52 tel
67           -rw-r--r--   1 aeb         37 Aug  6 23:53 tel2
68           $ mv tel tel1
69           $ ls -l
70           total 3
71           drwxr-xr-x   2 aeb       1024 Aug  6 23:51 bin
72           -rw-r--r--   1 aeb         37 Aug  6 23:52 tel1
73           -rw-r--r--   1 aeb         37 Aug  6 23:53 tel2
74           $ diff tel1 tel2
75           $ rm tel1
76           $ grep maja tel2
77           maja    0501-1136285
78           $
79
80       Here typing Control-D ended the session.
81
82       The  $  here was the command prompt—it is the shell's way of indicating
83       that it is ready for the next command.  The prompt can be customized in
84       lots  of ways, and one might include stuff like username, machine name,
85       current directory, time, and so on.  An assignment PS1="What next, mas‐
86       ter? " would change the prompt as indicated.
87
88       We see that there are commands date (that gives date and time), and cal
89       (that gives a calendar).
90
91       The command ls lists the contents of the current directory—it tells you
92       what  files  you  have.  With a -l option it gives a long listing, that
93       includes the owner and size and date of the file, and  the  permissions
94       people  have  for  reading  and/or changing the file.  For example, the
95       file "tel" here is 37 bytes long, owned by aeb and the owner  can  read
96       and  write  it,  others can only read it.  Owner and permissions can be
97       changed by the commands chown and chmod.
98
99       The command cat will show the contents of a file.  (The  name  is  from
100       "concatenate and print": all files given as parameters are concatenated
101       and sent to  "standard  output"  (see  stdout(3)),  here  the  terminal
102       screen.)
103
104       The command cp (from "copy") will copy a file.
105
106       The command mv (from "move"), on the other hand, only renames it.
107
108       The  command  diff lists the differences between two files.  Here there
109       was no output because there were no differences.
110
111       The command rm (from "remove") deletes the file, and be careful! it  is
112       gone.  No wastepaper basket or anything.  Deleted means lost.
113
114       The  command  grep (from "g/re/p") finds occurrences of a string in one
115       or more files.  Here it finds Maja's telephone number.
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117   Pathnames and the current directory
118       Files live in a large tree, the file hierarchy.  Each  has  a  pathname
119       describing  the  path  from the root of the tree (which is called /) to
120       the file.  For example, such a full pathname  might  be  /home/aeb/tel.
121       Always  using  full  pathnames would be inconvenient, and the name of a
122       file in the current directory may be abbreviated  by  giving  only  the
123       last  component.   That  is why /home/aeb/tel can be abbreviated to tel
124       when the current directory is /home/aeb.
125
126       The command pwd prints the current directory.
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128       The command cd changes the current directory.
129
130       Try alternatively cd and pwd commands and explore cd usage:  "cd",  "cd
131       .", "cd ..", "cd /", and "cd ~".
132
133   Directories
134       The command mkdir makes a new directory.
135
136       The  command  rmdir  removes  a directory if it is empty, and complains
137       otherwise.
138
139       The command find (with a rather baroque syntax) will  find  files  with
140       given  name or other properties.  For example, "find . -name tel" would
141       find the file tel starting in the present directory  (which  is  called
142       .).  And "find / -name tel" would do the same, but starting at the root
143       of the tree.  Large searches on a multi-GB disk will be time-consuming,
144       and it may be better to use locate(1).
145
146   Disks and filesystems
147       The  command  mount  will  attach the filesystem found on some disk (or
148       floppy, or CDROM or so) to the big filesystem  hierarchy.   And  umount
149       detaches  it again.  The command df will tell you how much of your disk
150       is still free.
151
152   Processes
153       On a UNIX system many user and  system  processes  run  simultaneously.
154       The  one  you  are talking to runs in the foreground, the others in the
155       background.  The command ps will show you which  processes  are  active
156       and  what numbers these processes have.  The command kill allows you to
157       get rid of them.  Without option this is a friendly request: please  go
158       away.   And "kill -9" followed by the number of the process is an imme‐
159       diate kill.  Foreground processes can often be killed  by  typing  Con‐
160       trol-C.
161
162   Getting information
163       There are thousands of commands, each with many options.  Traditionally
164       commands are documented on man pages, (like this one), so that the com‐
165       mand  "man  kill" will document the use of the command "kill" (and "man
166       man" document the command "man").   The  program  man  sends  the  text
167       through  some  pager,  usually less.  Hit the space bar to get the next
168       page, hit q to quit.
169
170       In documentation it is customary to refer to man pages  by  giving  the
171       name  and section number, as in man(1).  Man pages are terse, and allow
172       you to find quickly some forgotten detail.  For newcomers an  introduc‐
173       tory text with more examples and explanations is useful.
174
175       A  lot  of  GNU/FSF  software  is provided with info files.  Type "info
176       info" for an introduction on the use of the program info.
177
178       Special   topics   are   often   treated   in    HOWTOs.     Look    in
179       /usr/share/doc/howto/en and use a browser if you find HTML files there.
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SEE ALSO

182       ash(1), bash(1), chsh(1), csh(1), dash(1), ksh(1), locate(1), login(1),
183       man(1),  xterm(1),  zsh(1),  wait(2),  stdout(3),  man-pages(7),  stan‐
184       dards(7)
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188Linux man-pages 6.05              2023-05-03                          intro(1)
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