Add simple ExecPipe() to be used with filesystem format work

pkgs/utils/execpipe.go

@@ -0,0 +1,46 @@
+package utils
+
+import (
+	"bytes"
+	"errors"
+	"os/exec"
+)
+
+// A simple ExecPipe() pipes exec.Cmd together - somewhat similar to how bash pipes "|" behave.
+// Each command's standard output is connected to the standard input of the next command
+// and the output of the final command is returned
+
+func ExecPipe(cmds ...*exec.Cmd) (pipeLineOutput []byte, pipeLineError error) {
+	// Require at least one command
+	if len(cmds) < 1 {
+		return nil, errors.New("Invalid argument")
+	}
+
+	// Collect the output from the command(s)
+	var output bytes.Buffer
+
+	lastIndex := len(cmds) - 1
+	for i, cmd := range cmds[:lastIndex] {
+		cmds[i+1].Stdin, _ = cmd.StdoutPipe()
+	}
+
+	// Final ---> output buffer
+	cmds[lastIndex].Stdout = &output
+
+	// Start each command
+	for _, cmd := range cmds {
+		if err := cmd.Start(); err != nil {
+			return output.Bytes(), err
+		}
+	}
+
+	// We should Wait() for each command to complete
+	for _, cmd := range cmds {
+		if err := cmd.Wait(); err != nil {
+			return output.Bytes(), err
+		}
+	}
+
+	// Return the output
+	return output.Bytes(), nil
+}