Bourne tutorial
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| Sh - the Bourne Shell Last Updated: Wed Aug 17 12:38:31 EDT 2011 Check out my other tutorials on the Unix Page , and my blog
Thanks to suggestions/correectons from: Ryan Penn Helmut Neujahr DJ Phasik Table of Contents Bourne Shell, and filename expansion Shell Concepts Verifying which shell you are running Shell basics Meta-characters and Filename expansion Finding the executable Quoting with the Bourne Shell Nested quotations Strong versus weak quoting Quoting over several lines Mixing quotation marks Quotes within quotes - take two Placing variables within strings Variables A subtle point The set command Environment Variables Special Environment Variables PATH - Sets searchpath HOME - Your home directory CDPATH - cd searchpath IFS - Internal Field Seperator PS1 - Normal Prompt PS2 - Secondary Prompt MAIL - Incoming mail MAILCHECK - How often to check for mail SHACCT - Accounting file MAILPATH - searchpath for mail folders Bourne Shell Variables - Alternate Formats Using quoting and shell variables Using curly braces with variables ${variable?value} - Complain if undefined ${variable-default} - Use default if undefined ${variable+value} - Change if defined Bourne Shell Tutorial http://www.grymoire.com/Unix/Sh.html 1 of 66
11/21/2011 12:03 PM ${variable=value} - Redefine if undefined Undefining Variables ${x:-y}, ${x:=y}, ${x:?y}, ${x:+y} forms Order of evaluation Special Variables in the Bourne Shell Positional Parameters $1, $2, ..., $9 $0 - Scriptname $* - All positional parameters $@ - All positional parameters with spaces $# - Number of parameters $$ - Current process ID $! - ID of Background job $? - error status $- Set variables Options and debugging Special options X - Bourne Shell echo flag V - Bourne Shell verbose flag Combining flags U - unset variables N - Bourne Shell non-execute flag E - Bourne Shell exit flag T - Bourne Shell test one command flag A - Bourne Shell mark for export flag K - Bourne Shell keyword flag H - Bourne Shell hash functions flag The $- variable - - Bourne Shell hyphen option Other options C - Bourne Shell command option S - Bourne Shell shell-session option I - Bourne Shell shell-interactive option R - Bourne Shell restricted shell option P - Bourne Shell privileged shell option unset Bourne Shell: Status, Pipes and branches Unnecessary process execution $@ versus ${1+$@} Status and Wasted Processes Simple Flow Control Changing Precedence Putting it all together Bourne Shell Flow Control Commands: If, While and Until Commands that must be first on the line While - loop while true Until - loop until true Bourne Shell Flow Control Commands For - Repeating while changing a variable Case - Checking multiple cases Break and continue Expr - Bourne Shell Expression Evaluator Bourne Shell Tutorial http://www.grymoire.com/Unix/Sh.html 2 of 66
11/21/2011 12:03 PM Arithmetic Operators Relational Operators Boolean Operators The string operator Precedence of the Operators Berkeley Extensions Bourne Shell -- Functions and argument checking Passing values by name Exiting from a function Checking the number of arguments UNIX conventions for command line arguments Checking for optional arguments Job Control Copyright 2001, 2005 Bruce Barnett and General Electric Company All rights reserved You are allowed to print copies of this tutorial for your personal use, and link to this page, but you are not allowed to make electronic copies, or redistribute this tutorial in any form without permission. How to build your own complex commands from the simple commands in the UNIX toolbox. This tutorial discusses of Bourne shell programming, describing features of the original Bourne Shell. The newer POSIX shells have more features. I first wrote this tutorial before the POSIX shells were standardized. So the information describe here should work in POSIX shells as it is a subset of the POSIX specifications. You're not getting the most out of UNIX if you can't write shell programs! Bourne Shell, and filename expansion This sections covers the Bourne shell. The manual pages are only 10 pages long, so it shouldn't be difficult to learn, right? Well, apparently I'm wrong, because most of the people I know learned one shell to customize their environment, and stayed with the C shell ever since. I understand the situation. It's hard enough to learn one shell language, and after struggling with one shell for a while, they are hesitant to learn another shell. After a few scripts, the new user decides the C shell is "good enough for now" and it ends right there. They never take the next step, and learn the Bourne shell. Well, perhaps this chapter will help. The Bourne shell is considered the primary shell in scripts. All UNIX systems have it, first of all. Second, the shell is small and fast. It doesn't have the interactive features of the C shell, but so what? Interactive features aren't much use in scripts. There are also some features the Bourne shell has that the C shell doesn't have. All in all, many consider the Bourne shell to be the best shell for writing portable UNIX scripts. Shell Concepts What is a shell, anyway? It's simple, really. The UNIX operating system is a complex collection of files and programs. UNIX does not require any single method or interface. Many different techniques can be used. The oldest interface, which sits between the user and the software, is the shell. Twenty five years ago many users didn't even have a video terminal. Some only had a noisy, large, slow hard-copy terminal. The shell was the interface to the operating system. Shell, layer, interface, these words all describe the same concept. By Bourne Shell Tutorial http://www.grymoire.com/Unix/Sh.html 3 of 66 11/21/2011 12:03 PM Yüklə 478,18 Kb. Dostları ilə paylaş:
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