Sometimes you cannot find what you need within the available documentation, you should therefore contact the discussion groups of Usenet with special help requests. The network offers tools and services that you should know and use before attempting the last chance of 'global' requests. The generic search engine searches, allow to find published pages that contain a specific combination of words, entered as a search string. This type of search usually allows to find information that is not very recent because it must have been catalogued by the search engines before being available. The available search engines are different and usually it is convenient to concentrate on a couple of them, by studying the correct syntax for the search expressions. Generally you should know how to request the presence of two words or the presence of some words together with the absence of other ones.

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Most of them are normally available with the distributions, but their inquiry may be a problem for people without experience. The simplest way to write something is the pure text. This is what happens with the 'readme' and similar files, or with all documentation that has been converted in this format for simplicity.

These files can be read by using two well known programs: more or less. The functions of these two programs are similar, even if the second one offers a large number of additional functions which we do not consider. For the normal usage, options are not required and, if no file is listed in the arguments, the data are read from the standard input. Once any of these programs has been started, the text of the file is listed according to commands, entered by pressing keys.

The approach is similar to that used by VI: some commands require pressing one or more keys in sequence; some other ones require an argument and in this case, they appear in the last screen line or in a window.

The table Table List of common and fundamental commands of more and less. The main difference between these two programs is that less can scroll text backwards also when the text is received from the standard input, whereas this is not possible with more.

Moreover less allows the use the arrow keys and the page-up and page-down keys to scroll the text and allows also to make backward searches. Tabella List of additional commands for less. The commands above present on the screen the list of current directories that probably is too long to be seen fully without using these two programs.

Almost all programs have a manual page , or man page. It is a brief document about the usage of that particular program, written in a relatively standard format. There are various sections of these manual pages, according to the type of information that they contain. It is possible to have multiple pages with the same name, included in different sections.

Sections of the mannual pages. When you want to refer to a manual page, you should enter its name followed be a number within parentheses, which specifies the section.

For instance, man 1 refers to the manual page with name man in the first section. Often in the documentation, this kind of references are used for programs, to provide immediately the information on that specific program. The documentation is accessed by using the program man which usually runs less , or more , to scan the document. It is the location of the manual pages of additional application programs add-on.

These directories are all subdivided or subdivisable in the same way. Each of the starting directories is referred to as mandir. Then each of them can also be subdivided according to differences among architectures. It can be used to distinguish among the manual pages of different languages or of different formats.

Actually, the character set is not included because by default is ISO Among other things, this file contains the arguments used with the programs called to format the text for display or printing. Notice the following extract:. Something that it is useful, if you use foreign languages, is the option -T of nroff and of geqn. By using it as in the example -Tlatin1 , it allows to view the accented characters in the translated manual pages.

The man program formats and prints to the standard output the manual page specified by name. The scrolling of the manual page text is done through an external program, called automatically by man.

Usually this is either more or less. Consequently the commands to scroll the text depend on the type of used program. If it is one of the two discussed above, the commands listed in the table If a number appears before the name of the command or of the argument, it means that one wants to get the manual page from a specific section, as described in the table It searches the page names of one or more manual pages for the names entered in the arguments.

The results of the search are directed to the standard output. Only full words are matched and displayed. It finds the description of one or more manual pages which contain the argument string the search is done only on the description, including the page name, and not on the content of the manual page 3.

The Info documentation is an hypertext implemented by Info files and readable by using the info program or Emacs. The Info documentation is organised in files which include nodes.

Each node has a name and represents an information unit. Since this is an hypertextual system, each node may include references to other nodes which contain additional or connected information. Almost all nodes contain at least standard references defined from the following items:. The other references can be organised in menus or 'cross-references'. Each Info file contains at least a main node: Top. The nodes are simply identified by using following notation:.

If you refer only to the node name, you implicitely refer also to the corresponding file; if you refer only to the file name, you implicitely refer to the node name called Top. The info executable allows the inquiry of Info files without the need to use Emacs.

It specifies an affitional path to be used for the search of Info files. It selects the menu option pappa that should be contained in the main node of the pippo file. To access the information contained in these file with the info executable, you should know some commands that are not always intuitive. These commands are entered by simply pressing the key of the corresponding letter or symbol.

Some of these commands require arguments that must be entered and followed by the [ Entry ] key. The most important commands can be found in the table List of the main info commands.

When you use an hypertext, it is very important to know how you can backtrack. In this case, the command l allows to go back and is especially useful after the selection of an help command such as h or?

The picture Picture The guide to the use of the Info documentation. The line before the last, the second from the bottom, displays again the name of the file and of the node, in addition to the node size expressed in rows and to the word All. The word All means in this case that the node appears completely in the space provided by the screen or by the window. The last screen line is used to provide information to the user and to allow the entry of arguments possibly required by some command.

At the beginning of each node, together with the name of the file and of the node, there are some standard references to other nodes. They are represented symbolically by the terms Next , Prev previous e Up parent.

The person who has defined the Info file has defined also which nodes can be referred to by the above words and accessible by using the corresponding commands n , p and u.

List of navigation commands based on standard references. The Up reference does not always refer to a main node Top of the file that is inquired, but to a node that at that time, for some reason, represents a main reference. The same approach applies to the Next and Prev references that reflect only a temporary sequence. The node text may be longer than the lines available on the screen or on the window. You can scroll the text by using the space bar to scroll down and the [ Canc ] key to scroll up.

However you should pay attention: if too many scrolls are used, it continues with other nodes, by using a predefined path that usually does not reflect the Next and Prev references mentioned before. List of the commands for the natural scroll of a document. An hypertext is useful to reach the desired information by using a non sequential path. The Info documents use two types of references in addition to the standard ones : The menu and the cross references. The menu options can be selected by using the command m followed by the node name; the cross references can be selected by using the command f followed by the node name.

It is useful to have two different commands because the names may be entered in a short format only a few letters , by entering only the latters that allow to distinguish them from other names. By separating the menu references from those that appear in the text, there are less possibilities of misanderstandings. List of the commands to select references.

To simplify the selection of the references included in the text of a node including the menu , you can use the [ Tab ] key to position the cursor at the beginning of the next item and the [ Enter ] key to select the node referred by the item where the cursor is positioned.

If you know exactly the name of a node that you want to reach, you can use the command g followed by the name of that node. During the navigation within the Info documentation, it is always useful to remember the command l which allows to go back to the previous node. Other useful commands. The HOWTO documents are not included as an integral part of the package, because they are additional guides with objectives that are wider that the simple documentation of a single package.

They contain unordered information in a question and reply format. They are included in the LDP project, meaning Linux documentation project. Appunti di informatica libera It should be possible to link to this page also with the name documentation. Performs a search forwards, according to the entered regular expression indicata. It brings you to a programmed instruction sequence. Selects the node corresponding to the reference where the cursor is positioned.


«a2», ex «Appunti di informatica libera», ex «Appunti Linux»

Most of them are normally available with the distributions, but their inquiry may be a problem for people without experience. The simplest way to write something is the pure text. This is what happens with the 'readme' and similar files, or with all documentation that has been converted in this format for simplicity. These files can be read by using two well known programs: more or less.


This introductive chapter could make you grin and it might look out of place in a document that certainly is not yet suitable for newbies. However, as the title suggests, it is a container of notes that might be useful to somebody, maybe to remove some wrong concept. To understand the structure of a computer, you can imagine the behaviour of a cook in his kitchen. The cook prepares some specialties, or dishes, that have been ordered to him, according to the descriptions of the corresponding recipes. The orders are issued by clients that request the cook's services because they have appetite. The cook, in order to work, puts down everything, ingredients and recipe, on the work table. On one side of the table there are some carved instructions that are always useful to the cook; especially those that the cook must perform whenever the kitchen is open: cleaning the table, checking all tools pots, skillets, knives, spoons etc.



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