4 ms·

I've always done (cmd 2>&1) > file to redirect stderr and stdout to a file. I always thought the parenthesis were necessary, but according to this I can ju

• rcsorensen 14y ago
  cmd is going to output to STDOUT and STDERR, which are file descriptors 1 and 2. In a basic shell command execution, those route out to the console. Reading from left to right: cmd Run command cmd. File descriptors: {1: /dev/console, 2:/dev/console} > file Open a file descriptor for "file" and copy it into our first file descriptor (stdout). File descriptors: {1: fopen('file'), 2: /dev/console } 2>&1 Copy the file descriptor stored in 1 (stdout) into 2 (stderr). File descriptors: {1: fopen('file'), 2: fopen('file')}
• anon987 14y ago
  > Does anyone know the rationale behind ordering of redirects? I can't give you an exact rationale, but my old shell scripting books from the 90's use the cmd > file 2>&1 notation. My personal belief is that it was for situations when you would do something like this: cmd > output.txt 2> errors.txt
• dredmorbius 14y ago
  In the first case, you're actually executing two shells. (cmd 2>&1) runs in its own subshell, and copies stderr to stdout. >file is interpreted in the parent shell, and copies stdout to 'file'. In the second instance, you run a single shell, first copying stdout to 'file', then copying stderr to the (redirected) stdout, that is, 'file'.
• ralph 14y ago
  It's read as "cmd, stdout to file, stderr to the same place as stdout".