Standard Input [stdin]
Normally in linux the standard input is the console prompt, however this can change and set to be a file for example within the next command
$ process_that_require_a_file_as_input < file_required_by_process.txt
In this case the standard input of input was defined to be a file instead of the command prompt
Standard output [stdout]
Also the standard output in linux is the console, which generarly displays the results from an executed command
$ date Sun Apr 16 08:53:44 EDT 2017
We can redirect the standard output using the placeholder >
Sample
$ date > date.txt
Standard error [stderr]
This stream displays errors and it could be redirected using the placeholder 2>
$ comamnd_that_fails 2> failure.txt
The &> placeholder
This symbol represent the standard output and the standard err, meaning that if we want to redirect both outputs we can do something like this
$ command_that_runs_and_have_sime_fails &> log.txt
This command will redirect either normal output and error output to the file log.txt
The Pipe |
This symbol is useful in order to send the output of a command and put it as input for another command
$ ps auz | grep process_name
This command will first execute the ps command and pass the output to the command grep in order to check for a process called process_name
The Append >>
This symbol is used to append data to a file
$ echo "this data will be appended " >> text.log
The Add >
This symbol is used to add data to a file, it will overwrite what was written before, use with caution
$ echo "this data will be add and will overwrite what was written before " > text.log