Automating frequent tasks

Automating frequent tasks

Creating a shell script
    Running a script under any shell
    Writing a short shell script: an example
    Passing arguments to a shell script
    Performing arithmetic and comparing variables
    Performing arithmetic on variables in the Korn shell

Sending a message to a terminal
    The echo command
    The print command (Korn shell only)
    More about redirecting input and output

Getting input from a file or a terminal
    Reading a single character from a file or a terminal
    Attaching a file to a file descriptor

What to do if something goes wrong
    Solving problems with the environment
    Solving problems with your script
    What to do if your shell script fails

Writing a readability analysis program: an example
    How to structure a program
    Making a command repeat: the for loop
    Getting options from the command line: getopts
    Repeating commands zero or more times: the while loop
    Repeating commands one or more times: the until loop
    Making choices and testing input
    Choosing one of two options: the if statement
    Different kinds of test
    Testing exit values
    The && and || operators
    Making multiway choices: the case statement
    Generating a simple menu: the select statement
    Expanding the example: counting words
    Making menus
    Assigning variables default values

Tuning script performance

How programs perform

How to control program performance
    Number of processes generated
    Number of data bytes accessed
    Shortening data files
    Shortening directory searches
    Directory-search order and the PATH variable
    Recommended ways to set up directories

Putting everything together
    Readability analysis
    Extending the example

Other useful examples
    Mail tools
        Count the number of messages in MMDF mail folder
        Print the header lines of every message in a folder
        Mail a large file, in pieces
    File tools
        Return the total size of a group of files
        Compress a batch of files concurrently
    Useful routines
        Locking files
    Context sensitive scripts