As just learning Linux friends, we get a command, do not know how to use, the general will first look at the command default parameter description, and then do not know is through the Man Command Access manual. Still can't find the method, on the Internet search, finally can't go to the big forum post. Because a lot of time to send posts estimated to be more long someone reply. Over time, the enthusiasm for learning Linux has been neglected. In fact, this is the most difficult to learn Linux.
The Linux command help, generally has 2 kinds, the command own code inside has the use help explanation, this is generally very concise, is too long, the program own size as well as the daily maintenance is inconvenient. Another is a CHM format file with Help files, similar to Windows. Below I say these 2 kinds of how to consult.
first, the process of internal help information
For example:
[Chengmo@centos5 ~]$ cat--help
usage:cat [OPTION] [FILE] ...
Concatenate FILE (s), or standard input, to standard output.
-A,--show-all equivalent To-vet
# ... Omit
[chengmo@centos5 ~]$ man-h man
, version 1.6d
Usage:man [-ADFHKTWW] [section] [M path] [p Pager] [-s list]
[-M system] [-p string] name ...
#...... Omitted
Here are 2 examples, using the parameters to get commands to use help, which we often use. Said Han off, began to digress ..., hehe
I want to say the command. Common parameter rules, generally if with a parameter is a character, then use: a "-" connection, if the following argument is more than one character is used: "--" connection. is not a "-" can not be followed by more than one character? This is the flexibility of Linux command parsing, and if you use multiple characters with a "-" connection, it splits it into multiple parameters. For example: Ls–al equivalent to Ls–a–l, if you use: Ls–-al then it will take al as a whole parameter.
Also, the General Linux command will use-H, or--help, as a command line to return command-line help information. Especially--help most, some command 2 support. This has become a habit. If you encounter a command that you won't use, try these 2 parameters.
Second, obtain the command external Help file (man-pages)
What is a man page (man-pages)
Under Windows, we often call the Help manual an ebook, a CHM file. The Help manual below Linux is generally called man-pages. They are stored in some Linux folders in a certain way, if you need to check, you can access the Man-pages Manual index, Common: Info,man (this article is mainly about), Xman and so on. Speaking of which, there must be a friend who would say: "Is it convenient to have a CHM under Windows, search, query, and presentation?" In the shell Terminal view, is not a large piece of text, alone boring, dense. Haha, I can say that it is also rich in content, support ordinary text, tables, pictures, and also is the search to locate the need for information super fast. It must be a few times faster than clicking through the mouse in Windows.
So why is it easy to manage and indexed faster? Next, let's take a look at Man-pages's specifications.
Man-pages directory and filename specification definition
Storage directory:
The first is the directory and the storage specification, where Linux documents are often placed in the directory specified by the MANPATH environment variable. Generally in:/usr/share/man this directory inside. The following structure is also defined in this directory:
[chengmo@centos5 man]$ ls bg el fr hu& nbsp; it. utf-8 man1 man2x man4 man6 man8 Pl. iso8859-2 ro sk zh_cn cs Fr. iso8859-1 id ja man1p man3 man4x man6x man8x Pl. utf-8 ru sl Zh_TW da es Fr. utf-8 it ko man1x man3p man5 man7 man9 nl pt ru.koi8-r SV de fi hr it. iso8859-1 man0p man2 man3x man5x man7x Pl pt_br ru. utf-8 TR #可以分为 <strong>2 class </strong>, one is man[*] directory, one is: EN,ZH_CN,PL. Iso8859-2 classes represent languages already regions, encoded directories
First of all, man[*] This kind of catalogue means meaning. Linux Help documentation, a particularly interesting one is that, according to the document, the different types, the sub domain (that is, the category), we will say that the category according to what points. There is a similar: ZH_CN pl. Iso8859-2 these. The document is also divided into languages. Geography. Character encoding. You can support unified commands, multiple language versions of documents, and geographies can be different, and you can specify character sets. such as: Zh_tw.big5 This means: Chinese _ Taiwan region. Documents encoded using the BIG5 character set.
Document Domain differentiation methods (that is, categories)
Let's look at the following table:
Field |
Describe |
Description |
1 |
User command |
Can be started by anyone, such as Env, CAT, man, touch document |
2 |
system call or Kernel function |
Functions provided by the kernel, such as link, sethostname, mkdir |
3 |
Library Program |
That is, library functions such as Acosh, Asctime, Btree, Locale |
4 |
Device-related information |
A special file in the/dev directory, such as zero null SDA |
5 |
File Format description |
As described in the/etc/passwd file format description under this category |
6 |
Game |
Help file for games |
7 |
Other |
Includes macro command packs, conventions, etc. such as ARP, boot, regex, Unix UTF8 |
8 |
System Management |
Can only be started by root such as Fdisk, fsck, Renice, RPM, yum |
9 |
Kernel |
A document for storing kernel routines |
N |
New Document |
May want to move to a more appropriate field |
O |
Old document |
may be retained for a period of time |
L |
Local document |
Related to this particular system |
If the document belongs to that type, it is placed under the manpath/language _ area. Character Set/man[n] directory. There is no regional language, the Representative is en English document. Directly below: Manpath/man[n], basically most of the documents are underneath this.
Give me a column:
Linux under the command is: passwd Modify the password information, each user can call, so it will be placed under the man1/directory
But at the same time,/ETC/PASSWD has a Save user account information profile, its format and description information document, will be placed in the/man5 directory. So according to the field (hereafter all called this, hehe) distinguish, will not appear the same name file wrong situation. The above mentioned: 1,2,3,4,5,7,8 These types are often used by us. If I want to know the meaning of the/dev/null device, I can get to: Man4 the directory below.
Help file format:
Just said, the directory storage format, the Help file has its format as well. First, the naming format:
[command name. Field]: The name is the name of the command, function, or file name, followed by a point and then the field character. For example: If passwd command documentation, file name is: Passwd.1, plus the directory stored as: Man1/passwd.1, if the corresponding passwd format description document, it will be: Man5/passwd.5. Look at the following example:
[chengmo@centos5 man5]$ ls p*
pam.5.gz pam_env.conf.5.gz passwd.5.gz png.5.gz pam.conf.5.gz pam_krb
5.5.gz pbm.5.gz pnm.5.gz
pam.d.5.gz pam_ldap.5.gz pgm.5.gz ppm.5.gz
#/usr/share/man/man5 All faces start with a P file, from which we know that it corresponds to those configuration file format descriptions.
#pam. d.5.gz is PAM.D directory structure Description pam.5.gz is PAM module structure description
From this inside, the. GZ end appears to have been compressed by gzip, and the Linux system has been compressed to save document storage space with documents. Just look at the time we need to unzip and then view. The contents of the document do not change.
A little more verbose:
Careful friend must see a problem, above shows: The man directory under the structure examples inside, in addition to man[n] and language area directory. There is also a category of categories: man1,man0p,man1p,man1x here Description:
Plus p: Indicates POSIX programmer program documentation
Add x: Represents x Windows desktop program documentation
0p: POSIX programmer some C header file libraries, such as: tcp.h,ulimit.h and other documentation
Man-pages File Content Format specification
Can quickly and easily query Linux documents, in addition to directory specifications and naming conventions. There is also a format specification for the contents of the document.
A text file, not in Word format, basic ASCII characters, what are the specifications?
Maybe friends would say, yes, it is a text file, edit a random txt file, you can be a Linux document, such as: You wrote a: testhellow.sh script, and then you write a text save as: Man/man1/testhellow.1 file. This is even a document.
You can find it by using the Linux indexing method. However: it is not a canonical document.
Canonical format documents are:
Book page content |
Description |
NAME |
Name, manual section number and date of release of the program or order |
Synopsis |
How to invoke a command with a complete list of all options and parameters |
descriptl0n |
Short summary of commands and their usage |
Return VALUES |
A program or library function returns a value, and an environment that produces a specific return value |
EXIT STATUS |
Often used as a substitute for the costume Turnvalus |
OPTIONS |
Alphabetical List of options and parameters, if any |
FILES |
A list of documents used or used by the command |
USAGE |
Concise syntax for the language of the program, if any |
Enviroment |
List of environment variables used or used by the command |
Diagnostics |
List of error messages generated by commands and their solutions |
NOTES |
cannot be subsumed under any other category of information |
Conforming to |
List any difficulties that the program follows, such as POSIX or ISO |
ALSO |
Cross-indexing and information related to commands |
BUGS |
Point out known bugs and bug features, and how to contact the author of the program to fix them |
AUTHOR |
The name of the author or maintainer of the command, possibly with an e-mail address or a URL address |
The documentation for the specification, if any, will contain the above node types. We illustrate the following:
[chengmo@centos5 ~]$ gtbl cat.1 | Gtbl | groff-tascii-man CAT (1) User commands CAT (1) NAME cat- Concatenate files and print on the standard output synopsis cat [OPTION] [File] ... DESCRIPTION concatenate FILE (s), or standard input, to
Standard output. Omit .... examples cat f-g omitted ... AUTHOR
written by Torbjorn Granlund and Richard M. Stallman. REPORTING BUGS report bugs to <bug-coreutils@gnu.org>.
COPYRIGHT copyright (C) 2006 Free Software Foundation, Inc., omitted .... ALSO the Full documentation to cat is maintained as a texinfo manual. If omitted .... Cat 5.97 March 2007 CAT (1)
Here I unzipped a cat.1.gz and then use the command to view the document format as shown above, you see a lot of commands, display a document, in the next section of the document query we will know why.
This is mainly about the Linux document structure, including directories, naming, already document names, formats, and so on. These are not mandatory and the system is hard to force to detect if your own documents are satisfied. However, if you have a document you want to add to the system index, follow the rules to do, will let management more than chaos. As the saying goes: Irregular radius. This is the reason. Oh, today said more long-winded, do not know whether to say clearly, this time to say the comparative theory, the next section of the actual retrieval of the document aspects.