What does the ampersand indicate in this bash command 1>&2
Quick one, 2>&1 redirects stderr to stdout, but what does the ampersand mean? I know if we had 2 > 1 it would output to a file named 1 , what does the ampersand do?
它将文件描述符1复制到文件描述符2中.FD2是stderr，FD1是stdout，因此它将输出到stderr而不是stdout。
2>&1 redirects standard error (file handle 2) to the same file that standard output (file handle 1) is currently going to.
It's also a position-dependent thing so:
prog >x 2>&1 >y
will actually send standard error to x and standard output to y as follows:
x ; x ; y ; The ampersand belongs to the "1", so the snippet really has three parts: "2", ">", "&1". They mean, respectively, "take the data from output stream 2 (which is standard error)", "redirect it", and the redirection target, which is output stream 1. So "&" here allows you to redirect to an existing stream, rather than to a file.
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