exec: add Command.ExtraFiles

Allows passing extra fds to the child process.

Fixes #2329

R=rsc, dsymonds
CC=golang-dev
https://golang.org/cl/5162050

1 files changed, 6 insertions, 0 deletions

diff --git a/src/pkg/exec/exec.go b/src/pkg/exec/exec.go
index 3b20f2008c..aaad50846e 100644
--- a/src/pkg/exec/exec.go
+++ b/src/pkg/exec/exec.go
@@ -63,6 +63,11 @@ type Cmd struct {
 	Stdout io.Writer
 	Stderr io.Writer
 
+	// ExtraFiles specifies additional open files to be inherited by the
+	// new process. It does not include standard input, standard output, or
+	// standard error. If non-nil, entry i becomes file descriptor 3+i.
+	ExtraFiles []*os.File
+
 	// SysProcAttr holds optional, operating system-specific attributes.
 	// Run passes it to os.StartProcess as the os.ProcAttr's Sys field.
 	SysProcAttr *syscall.SysProcAttr
@@ -224,6 +229,7 @@ func (c *Cmd) Start() os.Error {
 		}
 		c.childFiles = append(c.childFiles, fd)
 	}
+	c.childFiles = append(c.childFiles, c.ExtraFiles...)
 
 	var err os.Error
 	c.Process, err = os.StartProcess(c.Path, c.argv(), &os.ProcAttr{