CS 497C - Introduction to UNIX
Lecture 5: Understanding the UNIX Command
Chin-Chih Chang chang@cs.twsu.edu

man: On-Line Help
* To understand details of commands, you can take on the UNIX documentation.
* man remains the most complete and authoritative guide to the UNIX system.
* To view the manual page of the C shell, you use man with csh as argument.
man csh

man: On-Line Help
* The entire man page pertaining to the csh command is dumped on the screen.
* Man presents the first page and pauses. This is done by sending its output 
  to a pager program, which displays the contents of a file one page (screen) 
  at a time.
* You press a key ([Spacebar] or [Enter]) to see the next page. To quit the 
  pager, press a q.

man: On-Line Help
* The pager is actually a UNIX command, and man is always preconfigured to be 
  used with a specific pager.
* UNIX systems use these pager programs:
 - more, Berkley's pager now available universally and a superior alternative 
   to the obsolete pg command.
 - less, the standard pager used by all Linux systems.
* When man displays a page, it doesn’t tell you the pager it uses. 

man: On-Line Help
* A pager has keys defined for viewing the previous and next page and 
  terminating the program. See Table 2.1.
* Some important man's pager commands are:
 - Next page - [Spacebar] or f
 - Previous page - b or p
 - Quit - q
 - Search for keyword - /keyword
 - Repeat search - n

man: On-Line Help
* You can see the man pages of multiple commands with a single invocation of 
  man.
man cp mv rm
* To know more about man, use the following:
man man

The man documentation
* Vendors organize the man documentation differently, but in general you'll 
  see eight sections of the UNIX manual. Later enhancements have added 
  subsections (like 1C, 1M, 3N etc.)
* The basic manual sections for SVR4 and Linux are shown in Table 2.2.
* Most of the commands you use are availale in Section 1, and man searches 
  the manuals starting from Section 1.

The man documentation
* We can use a number option to specify the section.
man 4 passwd
* You can specify multiple section numbers and multiple commands to look up.
man 2 mount 4 passwd
* The structure of the man page is divided into a number of compulsory and 
  optional sections where each section is preceded by a header.

Understanding a man Page
* The command headers are:
 - NAME - command name and its function
 - SYNOPSIS - arguments and options
 - DESCRIPTION - detailed explanation
 - EXAMPLES - examples of command usage
 - FILES - related files
 - SEE ALSO - related commands
 - DIAGNOSTICS - error messages
 - BUGS - errors that haven't been fixed yet
 - AUTHOR(S) - author(s) of the command

Info: The Texinfo Document
* Many systems also support the Textinfo documentation (we'll call it the 
  info documentation).
* The info is invoked with the command name:
info tar
* You'll now see an emacs-type interface describing the table of contents.

Info: The Texinfo Document
* Info document is organized in nodes where one node represents a section of 
  text at a certain level.
* Multilevel documents resemble the hypertext documents that are found in the 
  World Wide Web.
* Within a page, you can use the [Page Up] and [Page Down] keys in the normal 
  way for paging.

Info: The Texinfo Document
* You can take the cursor to any of these lines and press [Enter].
* To return to the previous level, press u (up).
* You can also move using p (previous) and n (next). To quit info, use q.
* If you get stuck, just quit info with q.
* When in doubt, press h to see the complete list of key sequences accepted by 
  the info reader.

whatis and apropos
* To get the short description of the command, use the whatis.
$ whatis cp
cp (1)           - copy files
* If you have no idea about the command to use in a given situation, you 
  should use the apropos command with one or more keywords.

whatis and apropos
* apropos gives you the name and short description from all manual sections 
  that contain the keyword.
$ apropos HTTP
* Both whatis and apropos can be used with multiple arguments. 
* If your keyword contains more than one word, use quotes.
$ apropos "regular expression"

whatis and apropos
* If you don't have the apropos command on your system, you can use man -k. 
* You can use man –f in place of whatis.
* Most Linux offer the --help option that displays a compact listing of all 
  options.
$ ls --help

Coming  Next
* Labor Day Holiday
* Review Chapter 2
* Do Self-Test of Chapter 2
* Turn in Homework 1 (September 5)
* General-Purpose Utilities