This is about UNIX features, POSIX ans Single UNIX specification, Understanding the man configuration of UNIX operating system

1. Unix Features, POSIX and
Single UNIX specification,
Understanding the man
configuration
SudhaRani.S
Computer Science & Engineering

2. Features of UNIX
Multiuser capability and background processing
Multitasking capability
Communication
Security, Simple
Portability

3. Features of UNIX
Time sharing
Command interpreter
Hierarchical file system
Simple command structure
Building-Block approach
UNIX toolkit
Pattern Matching

4. Features of UNIX
File security and protection
DOS-UNIX interface
System administration and job accounting
Tools and utilities
Shell and shell programming

5. Features of UNIX
Online documentation
Availability of 4GL and RDBMS
Library of application packages
Text processing
Graphics
Operational units

6. POSIX and Single UNIX Specification
POSIX (Portable Operating System Interface for computer
Environments) refers to operating system based on UNIX.
Developed at IEEE.
Refers to Operating System based on UNIX.
POSIX.1 - C application programming interface, the system calls

7. POSIX and Single UNIX Specification
POSIX.2 - deals with the Shell and Utilities.
POSIX 4 - thread management.
Unification of two standards (POSIX.1 & POSIX.2) known as Single
UNIX Specification(SUSV3). “Write once, adopt everywhere” once the
software has been developed on any POSIX, it can be easily ported to
another POSIX UNIX machine with lesser modifications.

8. Understanding the man configuration
 The UNIX man pages (man is short for manual ) cover every command available.
 To search for a man page, enter man followed by the name of the command to find .
 For example
man ls
 Man searches the manuals starting from section 1. Depending on the UNIX flavour we
need to use the prefix –s option to the section number
man 4 passwd //passwd alos occurs in section 4
man –s4 passwd // solaris uses the –s option

9. Understanding the man configuration
This displays the documentation for a configuration file
named /etc/passwd from section 4.
There’s also an entry for passwd in section 1 using man
passwd (without the section number)
man passwd

10. Understanding the man page
A man page is divided into a number of
compulsory and optional sections. It holds
NAME,SYNOPSIS,DESCRIPTION.
NAME – one line introduction to the command
Wc – displays a count of lines, words and
characters in a file

11. Understanding the man page
SYNOPSIS – syntax used by the command
Wc [-c | -m| -C ] [-lw] [file ….]
Where - c is count bytes
-m and –C is count characters
-l count lines
-w count words
DESCRIPTION – provides a detailed description
Description about wc in detail

12. Using man to Understand man
 man man is used to view its own documentation. Viewing man pages with man
 The variable PAGER controls the pager man uses and if you set it to less then man
will use less as its pager.
PAGER = less; export PAGER
Man wc
 To evaluate the value of PAGER, use the command echo $PAGER. This valid only for
the current session.

13. Further help with man
The POSIX specification requires man to support only one option –k
It searches a summary database and prints a one line description of
the command.
To know what awk does, use man command
$ man –k awk