Learning Linux Shell Scripting - Second Edition

Redirection

When a file descriptor is assigned to something other than a terminal, this is called I/O redirection. The shell performs the redirection of output to a file by closing the standard output file descriptor 1 (the Terminal) and then assigning that descriptor to the file. When redirecting standard input, the shell closes file descriptor 0 (the Terminal) and assigns that descriptor to a file. The Bash shells handle errors by assigning a file to file descriptor 2.The following command will take input from the sample.txt file:

    $ wc  <  sample.txt  

The preceding command will take content from the sample.text file. The wc command will print the number of lines, words, and characters in the sample.txt file. This command will redirect output ...