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Bash — pipes and redirections

stdin,stdout and stderr

When bash starts creates three file descriptors, these file descriptors point not to a file but in a terminal device usually in the format of /dev/tty[n]

stdin: file descriptor 0, stdin stands for standard input and means incoming to the terminal data, the standard device to enter data to the terminal is the keyboard.

stdout: file descriptor 1, stdout stands for standard output and means printing to the terminal normal messages, or text.

stderr: file descriptor 2, stderr stands for standard error and means printing error messages to the terminal.

redirecting output

The stdout and stderr can redirected to a file if we want, to do this we need to use redirection operators

The >operator

The > operator redirects the process output to a file, if the file does not exist will be created, if exists will be overwriten.

command > file.txt

Another way to do this is to write the full version, using the file descriptor

command 1> file.txt

The >>operator

The >> operator redirects the process output to a file, if the file does not exist will be created…