Tudásbázis

Bash output redirection

There are 3 built-in file descriptors: stdin, stdout and stderr (std=standard).

Basic

    0/1/2 references stdin/stdout/stderr
    >/2> redirects stdout/stderr, where > is taken as 1>
    &1/&2 references stdout/stderr
    &> redirects everything
    > creates or overwrites a file
    >> creates or appends to a file
    < reads from a file, where < is taken as 0<

Note: You should be pretty sure of what a command is doing if you are going to wipe it's output.

Redirecting Examples

    stdout to file: ls -l > ls-l.txt
    stderr to file: grep da * 2> grep-errors.txt
    one to another: grep da * 1>&2
    everything: do_stuff &> /dev/null
    combined: command < input-file > output-file, reads from input-file and writes stdout to output-file