[bash] How to redirect and append both stdout and stderr to a file with Bash?

To redirect stdout to a truncated file in Bash, I know to use:

cmd > file.txt

To redirect stdout in Bash, appending to a file, I know to use:

cmd >> file.txt

To redirect both stdout and stderr to a truncated file, I know to use:

cmd &> file.txt

How do I redirect both stdout and stderr appending to a file? cmd &>> file.txt did not work for me.

In Bash you can also explicitly specify your redirects to different files:

cmd >log.out 2>log_error.out

Appending would be:

cmd >>log.out 2>>log_error.out

This should work fine:

your_command 2>&1 | tee -a file.txt

It will store all logs in file.txt as well as dump them on terminal.

There are two ways to do this, depending on your Bash version.

The classic and portable (Bash pre-4) way is:

cmd >> outfile 2>&1

A nonportable way, starting with Bash 4 is

cmd &>> outfile

(analog to &> outfile)

For good coding style, you should

• decide if portability is a concern (then use classic way)
• decide if portability even to Bash pre-4 is a concern (then use classic way)
• no matter which syntax you use, not change it within the same script (confusion!)

If your script already starts with #!/bin/sh (no matter if intended or not), then the Bash 4 solution, and in general any Bash-specific code, is not the way to go.

Also remember that Bash 4 &>> is just shorter syntax — it does not introduce any new functionality or anything like that.

The syntax is (beside other redirection syntax) described here: http://bash-hackers.org/wiki/doku.php/syntax/redirection#appending_redirected_output_and_error_output

In Bash 4 (as well as ZSH 4.3.11):

cmd &>>outfile

just out of box

Try this

You_command 1>output.log  2>&1

Your usage of &>x.file does work in bash4. sorry for that : (

Here comes some additional tips.

0, 1, 2...9 are file descriptors in bash.

0 stands for stdin, 1 stands for stdout, 2 stands for stderror. 3~9 is spare for any other temporary usage.

Any file descriptor can be redirected to other file descriptor or file by using operator > or >>(append).

Usage: <file_descriptor> > <filename | &file_descriptor>

Please reference to http://www.tldp.org/LDP/abs/html/io-redirection.html

I am surprised that in almost ten years, no one has posted this approach yet:

If using older versions of bash where &>> isn't available, you also can do:

(cmd 2>&1) >> file.txt

This spawns a subshell, so it's less efficient than the traditional approach of cmd >> file.txt 2>&1, and it consequently won't work for commands that need to modify the current shell (e.g. cd, pushd), but this approach feels more natural and understandable to me:

1. Redirect stderr to stdout.
2. Redirect the new stdout by appending to a file.

Also, the parentheses remove any ambiguity of order, especially if you want to pipe stdout and stderr to another command instead.

Edit: To avoid starting a subshell, you instead could use curly braces instead of parentheses to create a group command:

{ cmd 2>&1; } >> file.txt

(Note that a semicolon (or newline) is required to terminate the group command.)