Redirecting CLI outputs using file descriptors

10 Mar, 2016 — 1 minute read — cli terminal

A terminal shell (bash, zsh) in Unix-like systems provide three standard file descriptors for any file in the filesystem.

STDIN (Standard Input) - file descriptor 0
STDOUT (Standard Output) - file descriptor 1
STDERR (Standard Error) - file descriptor 2

There are other cool things you can do with file descriptors but this post is just as a quick guide to some specific use cases - which is to redirect terminal outputs.

Let's see what we can do with the default file descriptors:

Redirect STDOUT of a command to a file.
```
ls 1> file_list
```
Even if we skip to mention file descriptor in our commands, it is defaulted to 1 (STDOUT)
```
ls > file_list
```
Redirect STDERR of a command to a file.
```
ls 2> file
```

Redirect both STDOUT and STDERR to a file.

ls -ltra &>file
# another way to do it
ls -ltra >&file

Redirect both STDOUT and STDERR to the same destination one after another.
```
# STDOUT is redirected first, followed by STDERR
ls -a >file 2>&1
```

This can be really handy when you're working on linux/osx terminals. Cheers!