exec: initial import

exec.go

@@ -0,0 +1,99 @@
+// package exec is a universal wrapper around the os/exec package.
+package exec
+
+import (
+ "bytes"
+ "errors"
+ "io"
+ "os/exec"
+)
+
+// Command returns a Cmd to execpute the named program with the given arguments.
+func Command(name string, args ...string) *Cmd {
+ return &Cmd{
+ Cmd: exec.Command(name, args...),
+ initalised: true,
+ }
+}
+
+// Cmd represents a command to be run.
+// Cmd must be created by calling Command.
+// Cmd cannot be reused after calling its Run or Start methods.
+type Cmd struct {
+ *exec.Cmd
+ initalised bool
+}
+
+// Run starts the specified command and waits for it to complete.
+//
+// The returned error is nil if the command runs, has no problems
+// copying stdin, stdout, and stderr, and exits with a zero exit
+// status.
+//
+// If the command fails to run or doesn't complete successfully, the
+// error is of type *ExitError. Other error types may be
+// returned for I/O problems.
+func (c *Cmd) Run(opts ...func(*exec.Cmd) error) error {
+ if err := c.Start(opts...); err != nil {
+ return err
+ }
+ return c.Wait()
+}
+
+// Start starts the specified command but does not wait for it to complete.
+//
+// The Wait method will return the exit code and release associated resources
+// once the command exits.
+func (c *Cmd) Start(opts ...func(*exec.Cmd) error) error {
+ if !c.initalised {
+ return errors.New("exec: command not initalised")
+ }
+ if err := applyDefaultOptions(c.Cmd); err != nil {
+ return err
+ }
+ if err := applyOptions(c.Cmd, opts...); err != nil {
+ return err
+ }
+ return c.Cmd.Start()
+}
+
+// Stdout specifies the process's standard output.
+func Stdout(w io.Writer) func(*exec.Cmd) error {
+ return func(c *exec.Cmd) error {
+ if c.Stdout != nil {
+ return errors.New("exec: Stdout already set")
+ }
+ c.Stdout = w
+ return nil
+ }
+}
+
+// Output runs the command and returns its standard output.
+func (c *Cmd) Output(opts ...func(*exec.Cmd) error) ([]byte, error) {
+ var b bytes.Buffer
+ err := c.Run(append(opts, Stdout(&b))...)
+ return b.Bytes(), err
+}
+
+// Dir specifies the working directory of the command.
+// If Dir is empty, the command executes in the calling
+// process's current directory.
+func Dir(dir string) func(*exec.Cmd) error {
+ return func(c *exec.Cmd) error {
+ c.Dir = dir
+ return nil
+ }
+}
+
+func applyDefaultOptions(c *exec.Cmd) error {
+ return nil
+}
+
+func applyOptions(c *exec.Cmd, opts ...func(*exec.Cmd) error) error {
+ for _, opt := range opts {
+ if err := opt(c); err != nil {
+ return err
+ }
+ }
+ return nil
+}