1 files changed, 160 insertions, 0 deletions
diff --git a/src/lib/exec.go b/src/lib/exec.go
new file mode 100644
index 000000000..ec48801f7
--- /dev/null
+++ b/src/lib/exec.go
@@ -0,0 +1,160 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package exec
+
+import (
+	"os";
+	"syscall";
+)
+
+const (
+	DevNull = iota;
+	Passthru;
+	Pipe;
+	MergeWithStdout;
+)
+
+type Cmd struct {
+	Stdin *os.FD;
+	Stdout *os.FD;
+	Stderr *os.FD;
+	Pid int;
+}
+
+// Given mode (DevNull, etc), return fd for child
+// and fd to record in Cmd structure.
+func modeToFDs(mode, fd int) (*os.FD, *os.FD, *os.Error) {
+	switch mode {
+	case DevNull:
+		rw := os.O_WRONLY;
+		if fd == 0 {
+			rw = os.O_RDONLY;
+		}
+		f, err := os.Open("/dev/null", rw, 0);
+		return f, nil, err;
+	case Passthru:
+		switch fd {
+		case 0:
+			return os.Stdin, nil, nil;
+		case 1:
+			return os.Stdout, nil, nil;
+		case 2:
+			return os.Stderr, nil, nil;
+		}
+	case Pipe:
+		r, w, err := os.Pipe();
+		if err != nil {
+			return nil, nil, err;
+		}
+		if fd == 0 {
+			return r, w, nil;
+		}
+		return w, r, nil;
+	}
+	return nil, nil, os.EINVAL;
+}
+
+// Start command running with pipes possibly
+// connected to stdin, stdout, stderr.
+// TODO(rsc): Should the stdin,stdout,stderr args
+// be [3]int instead?
+func OpenCmd(argv0 string, argv, envv []string, stdin, stdout, stderr int)
+	(p *Cmd, err *os.Error)
+{
+	p = new(Cmd);
+	var fd [3]*os.FD;
+
+	if fd[0], p.Stdin, err = modeToFDs(stdin, 0); err != nil {
+		goto Error;
+	}
+	if fd[1], p.Stdout, err = modeToFDs(stdout, 1); err != nil {
+		goto Error;
+	}
+	if stderr == MergeWithStdout {
+		p.Stderr = p.Stdout;
+	} else if fd[2], p.Stderr, err = modeToFDs(stderr, 2); err != nil {
+		goto Error;
+	}
+
+	// Run command.
+	p.Pid, err = os.ForkExec(argv0, argv, envv, fd);
+	if err != nil {
+		goto Error;
+	}
+	if fd[0] != os.Stdin {
+		fd[0].Close();
+	}
+	if fd[1] != os.Stdout {
+		fd[1].Close();
+	}
+	if fd[2] != os.Stderr && fd[2] != fd[1] {
+		fd[2].Close();
+	}
+	return p, nil;
+
+Error:
+	if fd[0] != os.Stdin && fd[0] != nil {
+		fd[0].Close();
+	}
+	if fd[1] != os.Stdout && fd[1] != nil {
+		fd[1].Close();
+	}
+	if fd[2] != os.Stderr && fd[2] != nil && fd[2] != fd[1] {
+		fd[2].Close();
+	}
+	if p.Stdin != nil {
+		p.Stdin.Close();
+	}
+	if p.Stdout != nil {
+		p.Stdout.Close();
+	}
+	if p.Stderr != nil {
+		p.Stderr.Close();
+	}
+	return nil, err;
+}
+
+func (p *Cmd) Wait(options uint64) (*os.Waitmsg, *os.Error) {
+	if p.Pid < 0 {
+		return nil, os.EINVAL;
+	}
+	w, err := os.Wait(p.Pid, options);
+	if w != nil && (w.Exited() || w.Signaled()) {
+		p.Pid = -1;
+	}
+	return w, err;
+}
+
+func (p *Cmd) Close() *os.Error {
+	if p.Pid >= 0 {
+		// Loop on interrupt, but
+		// ignore other errors -- maybe
+		// caller has already waited for pid.
+		w, err := p.Wait(0);
+		for err == os.EINTR {
+			w, err = p.Wait(0);
+		}
+	}
+
+	// Close the FDs that are still open.
+	var err *os.Error;
+	if p.Stdin != nil && p.Stdin.Fd() >= 0 {
+		if err1 := p.Stdin.Close(); err1 != nil {
+			err = err1;
+		}
+	}
+	if p.Stdout != nil && p.Stdout.Fd() >= 0 {
+		if err1 := p.Stdout.Close(); err1 != nil && err != nil {
+			err = err1;
+		}
+	}
+	if p.Stderr != nil && p.Stderr != p.Stdout && p.Stderr.Fd() >= 0 {
+		if err1 := p.Stderr.Close(); err1 != nil && err != nil {
+			err = err1;
+		}
+	}
+	return err;
+}
+