In bash, if you put:
ls /Users/*/.ssh/id_rsa 2>&1 > rsa-keys.log
…you’re redirecting stderr to the stdout’s destination while stdout is still sending output to the screen. So any permission errors encountered will go to the screen, not to rsa-keys.log.
From the bash manpage:
==================
Note that the order of redirections is significant. For example, the command
ls > dirlist 2>&1
directs both standard output and standard error to the file dirlist, while the command
ls 2>&1 > dirlist
directs only the standard output to file dirlist, because the standard error was duplicated from the standard output before the standard output was redirected to dirlist.
==================
Commands given to the shell are evaluated and processed in a specific order and fashion, and this is one quirk of that that many people are unaware of.
What distro uses /Users instead of /home? Doesn’t that break the standard?
MacOS
I used macs for 15 years I really should have known that lol.
Playskool
As true as this can be, it’s counterintuitive.
What would be more intuitive? It seems to me to be a
a=1 b=a a=2
Where you’d expect b to be 1, which is the case for bash.
In bash if you want to redirect both stderr and stdout to file you can use
&>filename.I never use more than one redirection to keep it simple. Stuff gets even weirder when you also use
<in the same linesenvsubstis a exception.
IMO
|& tee dirlistis easier to manageThis is a Bash thing?
https://www.man7.org/linux/man-pages/man1/bash.1.html
Pipelines A pipeline is a sequence of one or more commands separated by one of the control operators | or |&. The format for a pipeline is:
[time [-p]] [ ! ] command1 [ [|⎪|&] command2 … ]
(…) If |& is used, command1’s standard error, in addition to its standard output, is connected to command2’s standard input through the pipe; it is shorthand for 2>&1 |. This implicit redirection of the standard error to the standard output is performed after any redirections specified by command1.
So it is a bash thing.
Just to be clear, because some seem to conflate Bash with Shell. If not specified, assume POSIX shell, that’s how /bin/sh is handled as well. And that has no
|&.True
But nowadays
/bin/shis often just a link to bashWhich puts Bash in POSIX compliance mode.
$ sh sh-5.2$ echo dfgsdfgfd |& tee /tmp/t dfgsdfgfd sh-5.2$ cat /tmp/t dfgsdfgfd sh-5.2$¯_(ツ)_/¯
Your way would spawn a whole extra process, but if you’re running Bash commands I suppose that doesn’t often matter.
For
&1to work don’t we need to be using some shell anyway?Yeah. The shell, plus whatever command (or commands) you tell the shell to run.
