Question

7. The pipeline operator | turns the standard output (aka. stdout) of a command into the standard input (aka. stdin) of the next one. How can I turn the standard error (aka. stderr), and only that, into the standard input? Do so by first redirecting stderr to stdout, then redirecting stdout to /dev/null, then using the pipeline. Do an example with a first command that yields an error (e.g., cd to a non-existing directory), and tr of some character to another as the second command.

Write it as an executable script file in #!/bin/bash

Answer 1

Command :

cd aaa 2>&1>/dev/null | tr a b

Explanation:

2>&1 redirects stderr(2) to stdout(1), & is used to specify 1 is a file descriptor not file.

>/dev/null sends it to /dev/null

| tr a b, Here | is a pipeline operator and tr a b, changes all a's to b's in the output.