CS 497C

1
CS 497C Introduction to UNIXLecture 5
Understanding the UNIX Command

• Chin-Chih Changchang_at_cs.twsu.edu

2
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

3
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.

4
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, Berkleys 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 doesnt tell you the
  pager it uses.

5
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 mans pager commands are
• Next page Spacebar or f
• Previous page b or p
• Quit q
• Search for keyword - /keyword
• Repeat search - n

6
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

7
The man documentation

• Vendors organize the man documentation
  differently, but in general youll 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.

8
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.

9
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 havent been fixed yet
• AUTHOR(S) author(s) of the command

10
Info The Texinfo Document

• Many systems also support the Textinfo
  documentation (well call it the info
  documentation).
• The info is invoked with the command name
• info tar
• Youll now see an emacs-type interface describing
  the table of contents.

11
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.

12
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.

13
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.

14
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

15
whatis and apropos

• If you dont 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

16
Coming Next

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