Korn Shell Script Writing

Source: www.osc.edu
Topic: Shell Programming

Short Desciption:
A shell script is an executable file which is executed by the. shell linebyline. It can contain the following:. UNIX commands. shell programming ...

 

Content Inside:
Korn Shell Script WritingPage 11Korn Shell Script WritingScience & Technology Support GroupHigh Performance ComputingOSC (Ohio Supercomputer Center)1224 Kinnear RoadColumbus OH 43212Page 22Basic 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 ExercisesPage 33Creating a Shell Script A shell script is an executable file which is executed by the shell linebyline. 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/shuses Bourne shell to execute script #!/bin/cshuses C shell to execute script etc... Page 44Executing a Shell ScriptThere are 3 ways to execute a shell script: 1."dot" method $ . scriptname2."just the name" method $ scriptname3.in the background$ scriptname &Page 55Executing 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 for scriptname chmod +x scriptname current directory (.) must be in PATH or else must use ./scriptnamePage 66Executing a Shell Script (cont.)cat list # a simple little shell scriptprint "A listing of $PWD " > list.outls l >> list.out For methods 2 and 3 the shell runs another copy of itself as a subprocess. Pictorially the difference between Methods 1 2 and 3 is: Page 77Functions Improves shell's programmability already in memory (unless autoloaded) modular programing Syntax: function functname {shell commands}orfunctname (){shell commands}Page 88Functions (cont.) Delete a function definition with $ unset f functname Display all defined functions: $ functionsPage 99Functions (cont.) Two important differences between functions and she ...

 

 

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