Move readFile and execCommand to seperate files (#4015)

Co-authored-by: Chester Cheung <cheung.zhy.csu@gmail.com>
Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

sdk/resource/host_id.go

@@ -17,8 +17,6 @@ package resource // import "go.opentelemetry.io/otel/sdk/resource"
 import (
 	"context"
 	"errors"
-	"os"
-	"os/exec"
 	"strings"
 
 	semconv "go.opentelemetry.io/otel/semconv/v1.17.0"
@@ -38,27 +36,6 @@ type fileReader func(string) (string, error)
 
 type commandExecutor func(string, ...string) (string, error)
 
-// nolint: unused  // This is used by the hostReaderBSD, gated by build tags.
-func readFile(filename string) (string, error) {
-	b, err := os.ReadFile(filename)
-	if err != nil {
-		return "", nil
-	}
-
-	return string(b), nil
-}
-
-// nolint: unused  // This is used by the hostReaderBSD, gated by build tags.
-func execCommand(name string, arg ...string) (string, error) {
-	cmd := exec.Command(name, arg...)
-	b, err := cmd.Output()
-	if err != nil {
-		return "", err
-	}
-
-	return string(b), nil
-}
-
 // hostIDReaderBSD implements hostIDReader.
 type hostIDReaderBSD struct {
 	execCommand commandExecutor

sdk/resource/host_id_exec.go

@@ -0,0 +1,29 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build bsd || darwin
+
+package resource // import "go.opentelemetry.io/otel/sdk/resource"
+
+import "os/exec"
+
+func execCommand(name string, arg ...string) (string, error) {
+	cmd := exec.Command(name, arg...)
+	b, err := cmd.Output()
+	if err != nil {
+		return "", err
+	}
+
+	return string(b), nil
+}

sdk/resource/host_id_readfile.go

@@ -0,0 +1,28 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build bsd || linux
+
+package resource // import "go.opentelemetry.io/otel/sdk/resource"
+
+import "os"
+
+func readFile(filename string) (string, error) {
+	b, err := os.ReadFile(filename)
+	if err != nil {
+		return "", nil
+	}
+
+	return string(b), nil
+}