To check that it's open on the current /dev/null file specifically (not /some/chroot/dev/null for instance), on Linux only (where /dev/stdin is implemented as a symlink to the file open on fd 0 instead of a special device which when open acts like a dup(0) in other systems). Same applies for compiling c programs using gcc. Can my c program be present in a string which i then compile using gcc by redirecting its input from a file to the string. Likewise, can i redirect the output of my c program to a string instead of stdout or any other file before. Redirection: One way to get input into a program or to display output from a program is to use standard input and standard output, respectively.All that means is that to read in data, we use scanf (or a few other functions) and to write out data, we use printf. When we need to take input from a file (instead of having the user type data at the keyboard) we can use input redirection. 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.
␡
Objectives
If you want to prevent the output from a program to appear anywhere redirect to /dev/null. Executing commands in an elevated bash process by writing to the standard input of its parent script process. Logging the output of remote commands on multiple ssh servers without delay.
Page 1 of 11Next >
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.
Save 35% off the list price* of the related book or multi-format eBook (EPUB + MOBI + PDF) with discount code ARTICLE. * See informit.com/terms
This chapter is from the book
Practical Guide to Linux Commands, Editors, and Shell Programming, A, 4th Edition
This chapter is from the book
This chapter is from the book
Practical Guide to Linux Commands, Editors, and Shell Programming, A, 4th Edition
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
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.