How to redirect standard error to a file

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In linux if I want to redirect standard error to a file, I can do this:

$ls -l /bin/usr 2> ls-error.txt

But when I try:

$echo ${foo:?"parameter is empty"} 2> ls-error.txt

The result in terminal is:

bash: foo: parameter is empty

It doesn't work! Can somebody explain why? I thought ${parameter:?word} would send the value of word to standard error.

echo ${foo:?"parameter is empty"} 2>ls-error.txt redirects the stderr of echo, but the error message is produced by the shell while expanding ${foo:?"parameter is empty"}.

You can get the result you want by redirecting a block (or a subshell) instead so that the shell's stderr is included in the redirection:

{ echo "${foo:?"parameter is empty"}"; } 2>ls-error.txt

Redirecting Error Messages from Command Prompt: STDERR , If you want to log to the same file: command1 >> log_file 2>&1. If you want different files: command1 >> log_file 2>> err_file. Or, you can redirect the output to one place, and the errors to another. dir > output.msg 2> output.err You can print the errors and standard output to a single file by using the "&1" command to redirect the output for STDERR to STDOUT and then sending the output from STDOUT to a file:

Try this command: ($echo ${foo:?"parameter is empty"}) 2> ls-error.txt

How to redirect both stdout and stderr to a file, How do I redirect stderr to a file? A. Bash and other modern shell provides I/O redirection facility. There are 3 default standard files (standard  In some of the cases you also wanted to be redirect standard error (stderr) to file instead of displaying them on to the screen. In order to redirect standard error stderr to file you need to use “2>” symbol followed by the name of the file. Syntax: command 2> error.log. 1. command 2> error.log.

In case you would like to redirect both sandard and error output, AND to still get these messages when executing your command, you can use the tee command:

$echo ${foo:?"parameter is empty"} |& tee -a ls-error.txt

BASH Shell: How To Redirect stderr To stdout ( redirect stderr to a , All about redirection. 3.1 Theory and quick reference. There are 3 file descriptors, stdin, stdout and stderr (std=standard). Basically you can: redirect stdout to a  Redirect standard output and error to file in UNIX Redirect Standard output to a file. Redirecting command output from terminal to a file. Append with >> (double greater than sign/right angle bracket). Standard error redirection. By default, we can not redirect Standard error to a file by using

BASH Programming, Each open file gets assigned a file descriptor. [2] The file descriptors for stdin, stdout, and stderr are 0, 1, and 2, respectively. For opening additional files,  To redirect standard error messages to a file, enter:

I/O Redirection, Even if we redirect the stdout to a file, we still see the error output in the screen, because we are redirecting just the standard output, not the  Redirecting the standard error (stderr) and stdout to file. Use the following syntax: $ command-name &>file. OR. $ command > file-name 2>&1. Another useful example: # find /usr/home -name .profile 2>&1 | more.

Understanding Shell Script's idiom: 2>&1, Delve deep into stdout, stderr, and pipes plus some neat tricks that you might not But we can redirect that output to a file using the > operator:. To redirect stderr as well, you have a few choices: Redirect stdout to one file and stderr to another file: command > out 2>error. Redirect stdout to a file ( >out ), and then redirect stderr to stdout ( 2>&1 ): command >out 2>&1. Redirect both to a file (this isn't supported by all shells, bash and