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1. Objectives

Learn how to use shell features to make your work faster and easier. All of the features covered in this chapter work with both bash and tcsh.

1. Jan 04, 2003  If you're not going to use them, then by all means redirect them to /dev/null - but if you leave them closed then some data file in your program may end up open on descriptor 2, and some library functions will write to descriptor 2 given sufficient provocation, thus.
2. In Stevens' UNIX Network Programming, he mentions redirecting stdin, stdout and stderr, which is needed when setting up a daemon. He does it with the following C code /. redirect stdin, stdout, and Stack Overflow.
3. Aug 01, 2019  Surely you've heard other talk about stderr or 'Standard Error'. Similarly there is 'stdout' or 'Standard Out'. But what do they mean. What are those numbers and what is redirection? Ever heard of.

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This chapter is from the book 

/path/to/program arg1 arg2 /dev/null 2 /dev/null The syntax 2&1 means 'Send output currently going to file descriptor 2 to the same place that output going to file descriptor 1 is going to'. is omitting the default of FD1, so it is semantically the same as 1, which might make 2 make more sense. Java MyProgram /dev/null 2&1. It is also possible to pipe the output of your program directly in to another program. This is done using the pipe character instead of the angle bracket. // Redirect standard output to input another program java MyProgram grep 'keyword' How to redirect input By default, standard input comes from the keyboard.

Linux Shell Features

Objectives

After reading this chapter you should be able to:

• List special characters and methods of preventing the shell from interpreting these characters

• Describe a simple command

• Understand command-line syntax and run commands that include options and arguments

• Explain how the shell interprets the command line

• Redirect output of a command to a file, overwriting the file or appending to it

• Redirect input for a command so it comes from a file

• Connect commands using a pipeline

• Run commands in the background

• Use special characters as wildcards to generate filenames

• Explain the difference between a stand-alone utility and a shell builtin

Standard Input Redirect From Dev Null Card

This chapter takes a close look at the shell and explains how to use some of its features. It discusses command-line syntax and describes how the shell processes a command line and initiates execution of a program. This chapter also explains how to redirect input to and output from a command, construct pipelines and filters on the command line, and run a command in the background. The final section covers filename expansion and explains how you can use this feature in your everyday work.

Except as noted, everything in this chapter applies to the Bourne Again (bash) and TC (tcsh) Shells. The exact wording of the shell output differs from shell to shell: What the shell you are using displays might differ slightly from what appears in this book. For shell-specific information, refer to Chapters 8 (bash) and 9 (tcsh). Chapter 10 covers writing and executing bash shell scripts.

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