Re^5: The importance of avoiding the shell

[BrowserUk]

The Windows default shell (cmd.exe) does not understand 2>&1

Say what?

[Corion]

At least on my machine, it doesn't:

C:\Users\Corion>perl -le "warn 'foo';print 'bar'"
foo at -e line 1.
bar

C:\Users\Corion>perl -le "warn 'foo';print 'bar'" >tmp.txt
foo at -e line 1.

C:\Users\Corion>perl -le "warn 'foo';print 'bar'" 2>&1 >tmp.txt
foo at -e line 1.

C:\Users\Corion>ver

Microsoft Windows [Version 6.1.7601]

C:\Users\Corion>

Update: And I think I've been using the shell direction wrong, because it understands it if I redirect the filehandles in a different order:

C:\Users\Corion>perl -le "warn 'foo';print 'bar'" >tmp.txt 2>&1

C:\Users\Corion>type tmp.txt
foo at -e line 1.
bar

I always think "First, redirect filehandle 2 to filehandle 1, then redirect the output to filehandle 1 to a file.". But that this is wrong and I need to do it the other way around.

[BrowserUk]

Update: And I think I've been using the shell direction wrong, because it understands it if I redirect the filehandles in a different order: ... But that this is wrong and I need to do it the other way around.

Indeed. It does seem somewhat backwards, but it has always been that way.

When 2>&1 is seen, stderr is redirected to wherever stdout is pointing at that time. If you then redirect stdout somewhere else, stderr is not then re-redirected.

So if you want to redirect both to the same place, you have to redirect stdout first; then 2>&1 does the expected thing.