man1/intro.1

   1 .\" Copyright (c) 2002 Andries Brouwer <aeb@cwi.nl>
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  23 .TH INTRO 1 2002-08-06 "Linux" "Linux User's Manual"
  24 .SH NAME
  25 intro \- Introduction to user commands
  26 .SH DESCRIPTION
  27 Linux is a flavor of Unix, and as a first approximation
  28 all user commands under Unix work precisely the same under
  29 Linux (and FreeBSD and lots of other Unix-like systems).
  30 .LP
  31 Under Linux there are GUIs (graphical user interfaces), where you
  32 can point and click and drag, and hopefully get work done without
  33 first reading lots of documentation.
  34 The traditional Unix environment
  35 is a CLI (command line interface), where you type commands to
  36 tell the computer what to do.
  37 That is faster and more powerful,
  38 but requires finding out what the commands are.
  39 Below a bare minimum, to get started.
  40 .SS "Login"
  41 In order to start working, you probably first have to login,
  42 that is, give your username and password.
  43 See also
  44 .BR login (1).
  45 The program
  46 .I login
  47 now starts a
  48 .I shell
  49 (command interpreter) for you.
  50 In case of a graphical login, you get a screen with menus or icons
  51 and a mouse click will start a shell in a window.
  52 See also
  53 .BR xterm (1).
  54 .SS "The shell"
  55 One types commands to the
  56 .IR shell ,
  57 the command interpreter.
  58 It is not built-in, but is just a program
  59 and you can change your shell.
  60 Everybody has her own favorite one.
  61 The standard one is called
  62 .IR sh .
  63 See also
  64 .BR ash (1),
  65 .BR bash (1),
  66 .BR csh (1),
  67 .BR zsh (1),
  68 .BR chsh (1).
  69 .LP
  70 A session might go like
  71
  72 .RS
  73 .nf
  74 .BI "knuth login: " aeb
  75 .BI "Password: " ********
  76 .BI "% " date
  77 Tue Aug  6 23:50:44 CEST 2002
  78 .BI "% " cal
  79      August 2002
  80 Su Mo Tu We Th Fr Sa
  81              1  2  3
  82  4  5  6  7  8  9 10
  83 11 12 13 14 15 16 17
  84 18 19 20 21 22 23 24
  85 25 26 27 28 29 30 31
  86
  87 .BI "% " ls
  88 bin  tel
  89 .BI "% " "ls \-l"
  90 total 2
  91 drwxrwxr-x   2 aeb       1024 Aug  6 23:51 bin
  92 -rw-rw-r--   1 aeb         37 Aug  6 23:52 tel
  93 .BI "% " "cat tel"
  94 maja    0501-1136285
  95 peter   0136-7399214
  96 .BI "% " "cp tel tel2"
  97 .BI "% " "ls \-l"
  98 total 3
  99 drwxr-xr-x   2 aeb       1024 Aug  6 23:51 bin
 100 -rw-r--r--   1 aeb         37 Aug  6 23:52 tel
 101 -rw-r--r--   1 aeb         37 Aug  6 23:53 tel2
 102 .BI "% " "mv tel tel1"
 103 .BI "% " "ls \-l"
 104 total 3
 105 drwxr-xr-x   2 aeb       1024 Aug  6 23:51 bin
 106 -rw-r--r--   1 aeb         37 Aug  6 23:52 tel1
 107 -rw-r--r--   1 aeb         37 Aug  6 23:53 tel2
 108 .BI "% " "diff tel1 tel2"
 109 .BI "% " "rm tel1"
 110 .BI "% " "grep maja tel2"
 111 maja    0501-1136285
 112 .BI "% "
 113 .fi
 114 .RE
 115 and here typing Control-D ended the session.
 116 The
 117 .B "% "
 118 here was the command prompt \(em it is the shell's way of indicating
 119 that it is ready for the next command.
 120 The prompt can be customized
 121 in lots of ways, and one might include stuff like user name,
 122 machine name, current directory, time, etc.
 123 An assignment PS1="What next, master? "
 124 would change the prompt as indicated.
 125 .LP
 126 We see that there are commands
 127 .I date
 128 (that gives date and time), and
 129 .I cal
 130 (that gives a calendar).
 131 .LP
 132 The command
 133 .I ls
 134 lists the contents of the current directory \(em it tells you what
 135 files you have.
 136 With a \-l option it gives a long listing,
 137 that includes the owner and size and date of the file, and the
 138 permissions people have for reading and/or changing the file.
 139 For example, the file "tel" here is 37 bytes long, owned by aeb
 140 and the owner can read and write it, others can only read it.
 141 Owner and permissions can be changed by the commands
 142 .I chown
 143 and
 144 .IR chmod .
 145 .LP
 146 The command
 147 .I cat
 148 will show the contents of a file.
 149 (The name is from "concatenate and print": all files given as
 150 parameters are concatenated and sent to "standard output", here
 151 the terminal screen.)
 152 .LP
 153 The command
 154 .I cp
 155 (from "copy") will copy a file.
 156 On the other hand, the command
 157 .I mv
 158 (from "move") only renames it.
 159 .LP
 160 The command
 161 .I diff
 162 lists the differences between two files.
 163 Here there was no output because there were no differences.
 164 .LP
 165 The command
 166 .I rm
 167 (from "remove") deletes the file, and be careful! it is gone.
 168 No wastepaper basket or anything.
 169 Deleted means lost.
 170 .LP
 171 The command
 172 .I grep
 173 (from "g/re/p") finds occurrences of a string in one or more files.
 174 Here it finds Maja's telephone number.
 175 .SS "Pathnames and the current directory"
 176 Files live in a large tree, the file hierarchy.
 177 Each has a
 178 .I "pathname"
 179 describing the path from the root of the tree (which is called /)
 180 to the file.
 181 For example, such a full pathname might be /home/aeb/tel.
 182 Always using full pathnames would be inconvenient, and the name
 183 of a file in the current directory may be abbreviated by only giving
 184 the last component.
 185 That is why "/home/aeb/tel" can be abbreviated
 186 to "tel" when the current directory is "/home/aeb".
 187 .LP
 188 The command
 189 .I pwd
 190 prints the current directory.
 191 .LP
 192 The command
 193 .I cd
 194 changes the current directory.
 195 Try "cd /" and "pwd" and "cd" and "pwd".
 196 .SS "Directories"
 197 The command
 198 .I mkdir
 199 makes a new directory.
 200 .LP
 201 The command
 202 .I rmdir
 203 removes a directory if it is empty, and complains otherwise.
 204 .LP
 205 The command
 206 .I find
 207 (with a rather baroque syntax) will find files with given name
 208 or other properties. For example, "find . \-name tel" would find
 209 the file "tel" starting in the present directory (which is called ".").
 210 And "find / \-name tel" would do the same, but starting at the root
 211 of the tree. Large searches on a multi-GB disk will be time-consuming,
 212 and it may be better to use
 213 .BR locate (1).
 214 .SS "Disks and Filesystems"
 215 The command
 216 .I mount
 217 will attach the filesystem found on some disk (or floppy, or CDROM or so)
 218 to the big filesystem hierarchy. And
 219 .I umount
 220 detaches it again.
 221 The command
 222 .I df
 223 will tell you how much of your disk is still free.
 224 .SS "Processes"
 225 On a Unix system many user and system processes run simultaneously.
 226 The one you are talking to runs in the
 227 .IR foreground ,
 228 the others in the
 229 .IR background .
 230 The command
 231 .I ps
 232 will show you which processes are active and what numbers these
 233 processes have.
 234 The command
 235 .I kill
 236 allows you to get rid of them. Without option this is a friendly
 237 request: please go away. And "kill \-9" followed by the number
 238 of the process is an immediate kill.
 239 Foreground processes can often be killed by typing Control-C.
 240 .SS "Getting information"
 241 There are thousands of commands, each with many options.
 242 Traditionally commands are documented on
 243 .IR "man pages" ,
 244 (like this one), so that the command "man kill" will document
 245 the use of the command "kill" (and "man man" document the command "man").
 246 The program
 247 .I man
 248 sends the text through some
 249 .IR pager ,
 250 usually
 251 .IR less .
 252 Hit the space bar to get the next page, hit q to quit.
 253 .LP
 254 In documentation it is customary to refer to man pages
 255 by giving the name and section number, as in
 256 .BR man (1).
 257 Man pages are terse, and allow you to find quickly some forgotten
 258 detail. For newcomers an introductory text with more examples
 259 and explanations is useful.
 260 .LP
 261 A lot of GNU/FSF software is provided with info files. Type "info info"
 262 for an introduction on the use of the program "info".
 263 .LP
 264 Special topics are often treated in HOWTOs. Look in
 265 .I /usr/share/doc/howto/en
 266 and use a browser if you find HTML files there.
 267 .\"
 268 .\" Actual examples? Separate section for each of cat, cp, ...?
 269 .\" gzip, bzip2, tar, rpm
 270 .SH "SEE ALSO"
 271 .BR standards (7)