Required UNIX shell scripting material

sunray · December 28, 2009, 12:55am

As I am new in UNIX , and I want to learn UNIX shell scripting.

where shall I get material for Scripting ( For basics fundamentals and production environmental scripts)

Kindly provide me ......................

pludi · December 28, 2009, 1:46am

2 good starting points are the Bash Guide for Beginners and the Advanced Bash-Scripting Guide. Mind tho, while the bash is POSIX compatible, it has quite some extensions that are not.

solaris_user · December 28, 2009, 4:58pm

Bash is not good shell because does not support POSIX instead leran Korn shell

pludi · December 28, 2009, 5:11pm

Wrong. The bash is as much POSIX compatible as the Korn Shell (ksh), as both are a super-set of the POSIX standard. True, the POSIX standard was derived from the Korn shell, but still both support it completely, only the extensions to it differ (and no very much at that). If you want something that has absolutely nothing to do with POSIX try the C Shell.

As a simple test: take any script that's fully POSIX compatible (without any ksh extensions) and run it with bash instead of the Korn Shell. I've yet to experience any differences.

thegeek · December 28, 2009, 10:29pm

You may also enjoy reading this: Linux Shell Scripting Tutorial - A Beginner's handbook

solaris_user · December 29, 2009, 4:19am

yep totally compatible

http://www.gnu.org/software/bash/manual/html_node/Bash-POSIX-Mode.html

pludi · December 29, 2009, 5:01am

Did you read it completely? (emphasis added)

"more closely" for me means it's already compatible, just not as strict.

As for the list of things that change, these are relevant for non-interactive use (aka "scripting"):

Non-interactive shells exit if filename in . filename is not found.

Non-interactive shells exit if a syntax error in an arithmetic expansion results in an invalid expression.

Function names must be valid shell names. That is, they may not contain characters other than letters, digits, and underscores, and may not start with a digit. Declaring a function with an invalid name causes a fatal syntax error in non-interactive shells.

A non-interactive shell exits with an error status if a variable assignment error occurs when no command name follows the assignment statements. A variable assignment error occurs, for example, when trying to assign a value to a readonly variable.

A non-interactive shell exits with an error status if the iteration variable in a for statement or the selection variable in a select statement is a readonly variable.

The . and source builtins do not search the current directory for the filename argument if it is not found by searching PATH.

Ad 12: that shouldn't be a problem, as I think it's pretty common to check if something is there before trying to access it
Ad 13: pretty much the same. It's like checking the value of the divisor before trying to divide by zero.
Ad 16: I can't image a situation where I'd need a function that has a '%' or '/' in it...
Ad 20: If you can't keep track of which variables are read-only and which aren't...
Ad 21: see above.
Ad 28: So it works the same as command lookup, which requires you to use the (IMO) more readable ". ./filename" instead of ". filename"

And while I myself prefer the Korn shell to bash, it isn't without incompatibilities itself, as the POSIX standard shell was based on ksh88, while the current, ksh93, features quite some changes.

sunray · December 29, 2009, 5:13am

Thanx to all of u.

Now I will start with basic shell fundamentals and syntax.