What does echo error 1 >& 2 do?
The 1 denotes standard output (stdout). The 2 denotes standard error (stderr). So 2>&1 says to send standard error to where ever standard output is being redirected as well.
Is stdout same as stderr?
stdout: Stands for standard output. The text output of a command is stored in the stdout stream. stderr: Stands for standard error. Whenever a command faces an error, the error message is stored in this stream.
How do I redirect to stderr?
The regular output is sent to Standard Out (STDOUT) and the error messages are sent to Standard Error (STDERR). When you redirect console output using the > symbol, you are only redirecting STDOUT. In order to redirect STDERR, you have to specify 2> for the redirection symbol.
What is stdout and stderr in C?
Stdout and stderr are standards in which stdout is fully buffered whereas stderr is not fully buffered because stdout will completely remove the messages or flushes whenever the program is asked to do explicitly and stderr writes the output message or error message immediately to the console or the window terminal.
How do I redirect stderr and stdout to a file in bash?
Bash executes the redirects from left to right as follows:
- >>file. txt : Open file. txt in append mode and redirect stdout there.
- 2>&1 : Redirect stderr to “where stdout is currently going”. In this case, that is a file opened in append mode. In other words, the &1 reuses the file descriptor which stdout currently uses.
What is difference between input redirection and output redirection?
Input/Output (I/O) redirection in Linux refers to the ability of the Linux operating system that allows us to change the standard input ( stdin ) and standard output ( stdout ) when executing a command on the terminal. By default, the standard input device is your keyboard and the standard output device is your screen.
How do I write or echo to stderr?
To write or echo to stderr, I normally use a custom function that redirects the output of the echo command to the standard error stream. The above script has a custom function called echo_stderr that performs the stderr redirect.
Why can’t I read from stdout or stderr?
Except in the special case of terminal devices open in read+write mode, stdout and stderr are usually not open for reading. They are meant to be streams that you write to. So reading from the file descriptor 1 will generally not work.
How to use 1 as the standard output in stderr?
Since 1is the standard output, you do not have to explicitly name it in front of an output redirection like >. Instead, you can simply type: echo This message goes to stderr >&2
What are stdin and stdout and stderr?
They are not stdin, stdout, stderr, they are special files that identify what files stdin, stdout, stderr go to (note that it’s different in other systems than Linux that have those special files). reading something from stdin means reading from file descriptor 0 (which will point somewhere within the file referenced by /dev/stdin ).