Korn Shell Script Writing

Source: www.osc.edu
Topic: Shell Programming

Short Desciption:
2 Basic Shell Programming • Creating a Shell Script • Executing a Shell Script • Functions • Precedence of Commands • eval • Shell Variables • Assigning Variable Names • • ...

 

Content Inside:
1 Korn Shell Script Writing Science & Technology Support Group High Performance Computing OSC (Ohio Supercomputer Center) 1224 Kinnear Road Columbus, OH  43212 2 Basic Shell Programming • Creating a Shell Script • Executing a Shell Script • Functions • Precedence of Commands • eval • Shell Variables • Assigning Variable Names • • Null Variables • Special Shell Variables • Parameter Substitution • Special Pattern Matching Features • Command Substitution • Exercises 3 Creating a Shell Script • A shell script is an executable file which is executed by the shell line-by-line. It can contain the following: -UNIX commands -shell programming statements -comments • Create using editor of choice • Can include a #! construct in first line of script to override login shell -#!/bin/sh usesBourneshell to execute script -#!/bin/csh uses C shell to execute script -etc. 4 Executing a Shell Script There are 3 ways to execute a shell script: 1."dot"  method $. scriptname 2."just the name" method $scriptname 3.in the background $scriptname& 5 Executing a Shell Script (cont.) • Method 1 runs the command as if you typed them in on the command line • Note that methods 2 and 3 require: -execute permission forscriptname chmod+xscriptname -current directory (.) must be in PATH or else must use ./scriptname 6 Executing a Shell Script (cont.) cat list #asimplelittle shell script print "Alistingof$PWD ">list.out ls-l>>list.out • For methods 2 and 3 the shell runs another copy of itself as asubprocess. Pictorially, the difference between Methods 1, 2, and 3 is: 7 Functions • Improves shells programmability -already in memory (unlessautoloaded) -modular programing • Syntax: function functname{ shell commands } or, functname () { shell commands } 8 Functions (cont.) • Delete a function definition wi ...

 

 

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