Author: Jeff Hobbs <email@example.com> State: Final Type: Project Tcl-Version: 8.5 Vote: Done Created: 19-May-2004 Post-History: Keywords: Tcl, redirection Tcl-Ticket: 957132
This TIP proposes adding a new redirection case '2>@1' that redirects the error channel to the output channel in open and exec. This would only be valid at the end of a pipeline.
Tcl is currently limited on how stderr can be managed from a command opened with open | or exec. This TIP adds the ability to simply combine the stderr stream with the stdout stream by adding a new output redirection case, 2>@1 (i.e. as in Bourne shell syntax), that is only ever valid as the last redirection item in a pipeline. This will enable simple capturing of stderr as well as stdout across platforms.
The behavior is similar to 2>@stdout, but that does not work across platforms. The difference is that directs to a real stdout file channel (which is not available in Windows wish for example), whereas 2>@1 would redirect to the output result for exec/open.
The intention is to handle the common case of wanting to capture stderr as well as stdout output from a single command. This operator is only valid as the last redirection operator. To redirect stderr of previous commands along with their stdout, use the preexisting |& pipe operator.
This is backwards compatible as 2>@1 currently raises an error that "1" is not a valid file id (Tcl does not create such file ids).
set fid [open "|$cmd 2>@1"] set result [exec $cmd 2>@1]
See SF Tcl Patch 957132 http://sf.net/tracker/?func=detail&aid=957132&group_id=10894&atid=310894 for details.
This document has been placed in the public domain.