I am reading this book – “Unix concepts and applications” written by the great author “Sumitabha Das”. This book is very good to start from the basics. If you wanna buy it , you can purchase it from Buy Unix Concepts And Applications from Flipkart.com .
It is very difficult to remember each shell command, even experts get confused with them sometimes. There’s an inbuilt documentation called as Man pages in Unix/Linux which practically provides the documentation of every command. You just have to type “man command” (without Quotes). What man command does,it searches for the documentation of the given command and display it on the shell through the pager program. Man documentation has been divided into several sections. As of present it is divided into 9 sections each having a collection of specific category. Sections are-
1. Executable programs or shell commands
2. System Calls
3. Library Calls
4. Special Files (Usually Found in /dev)
5.File Formats and Coventations
8. System Admin Commands
9. Kernel Routines
Most of the commands are available in the section 1. When you call the man documentation such as “man wc” man will look for the documentation of the wc command in the sections starting from section number 1. As soon as it finds it, it will stop looking further and will display the documentation of the wc from the section 1. There are many commands which are available in the multiple sections of the man documentation. For example passwd command is available in both section 1 and section 4. To locate the documetation section wise you should type the section number as an argument. Ex- “man 4 passwd” . This will display the man page of passwd form the section 4 not from the section 1.