Standard streams

Strandard stream allows the machine to interact with the external periferals. Hence they are file that represents streams stored usually in the /dev (device) directory. They can handle input, output and error streams produced by the processes i.e.

• Standard input|STDIN - file handle that your process reads to get information from you i.e. keyboard or mouse input.
• Standard output|STDOUT - your process writes conventional output to this file handle.
• Standard error|STDERR - your process writes diagnostic output to this file handle.

That's mostly by convention .

Examples

executable   <inputfile.txt    2>errorfile.txt  |  grep nice_work

which will:

• create a process for executable.
• open ./inputfile.txt as your standard input (file handle 0).
• open ./errorfile.txt as your standard error (file handle 2).
• create another process for grep.
• attach the standard output of executable to the standard input of grep.