Input Output and Redirection

Input Output and Redirection

1. What is File Descriptor?

In Unix and related computer operating systems, a file descriptor (FD) is an abstract indicator used to access a file or other input/output resource, such as a pipe or network socket. File descriptors form part of the POSIX application programming interface.

1. Input/Output Types

I/O Name Abbreviation File Descriptor

Standard Input stdin 0

Standard Output stdout 1

Standard Error stderr 2

1. Redirection

> Redirects standard output to a file (Overwrite existing content)

>>Redirects standard output to a file (Append to any existing content)

< Redirects input from a file to a command

1. Example

ls -l > file.txt - this will put Output of ls command to file.txt (with overwriting)

2 > /dev/null - this will put any error happens to the null place

sort < file.txt - this will take the input from the file.txt for the sort command

1. Transfer File Over Network

use scp command