The expression 2>&1 copies file descriptor 1 to location 2, so any output written to 2 ("standard error") in the execution environment goes to the same file originally described by 1 ("standard output").

Jun 11, 2015 · Bash typically uses either &> or 2>&1. IMHO, neither is "perfect", so I recommend forgetting about that nonsense. Realistically, which one you should use depends on what you are trying to do. 2>&1 merges stderr with stdout, which can be …

Mar 23, 2023 · 2>&1 is an I/O redirection operator used in Bash that redirects the stderr stream to the same destination as the stdout stream. In other words, it merges the error output with the regular output, making it easier to capture and handle errors. …

So basically you switched STDOUT and STDERR, these are the steps: Redirect file descriptor 1 to file descriptor 2. If we wouldn't have saved the file descriptor in 3 we would lose the target. Redirect file descriptor 2 to file descriptor 3. Now file descriptors one and two are switched.

Bash is an sh -compatible command language interpreter that executes commands read from the standard input or from a file. Bash also incorporates useful features from the Korn and C shells (ksh and csh). Bash is intended to be a conformant implementation of the Shell and Utilities portion of the IEEE POSIX specification (IEEE Standard 1003.1).

Redirection allows commands’ file handles to be duplicated, opened, closed, made to refer to different files, and can change the files the command reads from and writes to. Redirection may also be used to modify file handles in the current shell execution environment.

Bash uses the value formed by expanding the rest of parameter as the new parameter; this is then expanded and that value is used in the rest of the expansion, rather than the expansion of the original parameter. This is known as indirect expansion.

Dec 28, 2014 · However, the bash manual Redirections section adds that: Of the two forms, the first is preferred. This is semantically equivalent to >word 2>&1 When using the second form, word may not expand to a number or -. If it does, other redirection operators apply (see Duplicating File Descriptors below) for compatibility reasons.

May 28, 2019 · 0>&1 (same as 0<&1 or <&1) adds 0 (stdin) to the list. It duplicates fd 1 to 0 as well (fd 0 is made to point to the same resource as pointed to by fd 1). Now, when doing > /dev/tcp/host/port in bash (like in ksh where the feature comes from), instead of doing a open(file, O_WRONLY), bash creates a TCP socket and connects it to host:port.

Jul 10, 2014 · The & is used on the right side to distinguish stdout (1) or stderr (2) from files named 1 or 2. So, 2>1 would end up creating a new file (if it doesn't exist already) named 1 and dump the stderr result in there.