Book Image

Linux Shell Scripting Essentials

By : Sinny Kumari, Khem Raj
Book Image

Linux Shell Scripting Essentials

By: Sinny Kumari, Khem Raj

Overview of this book

Table of Contents (15 chapters)
Linux Shell Scripting Essentials
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Standard I/O and error streams


In shell programming, there are different ways to provide an input (for example, via a keyboard and terminal) and display an output (for example, terminal and file) and error (for example, terminal), if any, during the execution of a command or program.

The following examples show the input, output, and error while running the commands:

  • The input from a user by a keyboard and the input obtained by a program via a standard input stream, that is terminal, is taken as follows:

    $ read -p "Enter your name:"
    Enter your name:Foo
  • The output printed on the standard output stream, that is terminal, is as follows:

    $ echo "Linux Shell Scripting"
    Linux Shell Scripting
  • The error message printed on the standard error stream, that is terminal, is as follows:

    $  cat hello.txt
    cat: hello.txt: No such file or directory

When a program executes, by default, three files get opened with it which are stdin, stdout, and stderr. The following table provides a short description of each of these...