man1/intro.1

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