add basic infrastructure for writing a checker

These are the first components to interact with the database in a
predefined way to write a checker instance.
CheckExec serves as an example implementing the Executor interface.

1 files changed, 38 insertions, 0 deletions

diff --git a/executor.go b/executor.go
new file mode 100644
index 0000000..ca8e5e2
--- /dev/null
+++ b/executor.go
@@ -0,0 +1,38 @@
+package monzero
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"os/exec"
+	"syscall"
+)
+
+// CheckExec runs a command line string.
+// The output is recorded completely and returned as one message.
+func CheckExec(check Check, ctx context.Context) CheckResult {
+	result := CheckResult{}
+
+	cmd := exec.CommandContext(ctx, check.Command[0], check.Command[1:]...)
+	output := bytes.NewBuffer([]byte{})
+	cmd.Stdout = output
+	cmd.Stderr = output
+	err := cmd.Run()
+	if err != nil {
+		if cmd.ProcessState == nil {
+			result.Message = fmt.Sprintf("unknown error when running command: %w", err)
+			result.ExitCode = 3
+			return result
+		}
+
+		status, ok := cmd.ProcessState.Sys().(syscall.WaitStatus)
+		if !ok {
+			result.Message = fmt.Sprintf("error running check: %w", err)
+			result.ExitCode = 2
+		} else {
+			result.ExitCode = status.ExitStatus()
+		}
+	}
+	result.Message = output.String()
+	return result
+}