Data Source: local_exec

Add new data source `local_exec`. This allows for the execution of a
specified command on the local system and retrieve it's output.

Resolves: #8

Author: abn

internal/provider/data_source_local_exec.go

@@ -0,0 +1,119 @@
+package provider
+
+import (
+	"crypto/sha1"
+	"encoding/hex"
+	"fmt"
+	"io/ioutil"
+	"os/exec"
+	"syscall"
+
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
+)
+
+func dataSourceLocalExec() *schema.Resource {
+	return &schema.Resource{
+		Read: dataSourceLocalExecRead,
+
+		Schema: map[string]*schema.Schema{
+			"command": {
+				Type:        schema.TypeList,
+				Description: "Command to execute",
+				Required:    true,
+				ForceNew:    true,
+				Elem:        &schema.Schema{Type: schema.TypeString},
+			},
+			"working_dir": {
+				Type:        schema.TypeString,
+				Description: "Directory to change into before executing provided command",
+				Optional:    true,
+				Default:     "",
+				ForceNew:    true,
+			},
+			"ignore_failure": {
+				Type:        schema.TypeBool,
+				Description: "If set to true, command execution failures will be ignored",
+				Optional:    true,
+				Default:     false,
+				ForceNew:    true,
+			},
+			"stdout": {
+				Type:     schema.TypeString,
+				Computed: true,
+			},
+			"stderr": {
+				Type:     schema.TypeString,
+				Computed: true,
+			},
+			"rc": {
+				Type:     schema.TypeInt,
+				Computed: true,
+			},
+		},
+	}
+}
+
+func dataSourceLocalExecRead(d *schema.ResourceData, _ interface{}) error {
+	exitCode := 0
+	command, args, _ := expandCommand(d)
+	ignoreFailure := d.Get("ignore_failure").(bool)
+
+	cmd := exec.Command(command, args...)
+	cmd.Dir = d.Get("working_dir").(string)
+
+	stdoutPipe, err := cmd.StdoutPipe()
+	if err != nil {
+		return err
+	}
+
+	stderrPipe, err := cmd.StderrPipe()
+	if err != nil {
+		return err
+	}
+
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+
+	stderr, _ := ioutil.ReadAll(stderrPipe)
+	stdout, _ := ioutil.ReadAll(stdoutPipe)
+
+	if err := cmd.Wait(); err != nil {
+		if exitError, ok := err.(*exec.ExitError); ok {
+			if status, ok := exitError.Sys().(syscall.WaitStatus); ok {
+				exitCode = status.ExitStatus()
+			} else {
+				// unable to retrieve exit code from error, use default
+				exitCode = -1
+			}
+		}
+
+		if !ignoreFailure {
+			return err
+		}
+	}
+
+	d.Set("stderr", string(stderr))
+	d.Set("stdout", string(stdout))
+	d.Set("rc", exitCode)
+
+	// use the checksum of (stdout, stderr, rc) to generate id
+	checksum := sha1.Sum(
+		append([]byte(stdout),
+			append([]byte(stderr),
+				[]byte(fmt.Sprintf("%d", exitCode))...)...))
+	d.SetId(hex.EncodeToString(checksum[:]))
+
+	return nil
+}
+
+func expandCommand(d *schema.ResourceData) (string, []string, error) {
+	execCommand := d.Get("command").([]interface{})
+	command := make([]string, 0)
+
+	for _, commandRaw := range execCommand {
+		command = append(command, commandRaw.(string))
+	}
+
+	return command[0], command[1:], nil
+}

internal/provider/data_source_local_exec_linux_test.go

@@ -0,0 +1,80 @@
+// +build linux
+
+package provider
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/resource"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
+)
+
+func TestLocalExecDataSource(t *testing.T) {
+	var tests = []struct {
+		stdout string
+		stderr string
+		rc     string
+		config string
+	}{
+		{
+			"hello",
+			"world",
+			"0",
+			`
+				data "local_exec" "command" {
+					command = ["sh", "-c", "echo -n hello; echo -n 1>&2 world"]
+				}
+			`,
+		},
+		{
+			"",
+			"",
+			"127",
+			`
+				data "local_exec" "command" {
+					command = ["sh", "-c", "exit 127"]
+                    ignore_failure = true
+				}
+			`,
+		},
+		{
+			"/tmp\n",
+			"",
+			"0",
+			`
+				data "local_exec" "command" {
+					command = ["pwd"]
+                    working_dir = "/tmp"
+				}
+			`,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run("", func(t *testing.T) {
+			resource.UnitTest(t, resource.TestCase{
+				Providers: testProviders,
+				Steps: []resource.TestStep{
+					{
+						Config: test.config,
+						Check: func(s *terraform.State) error {
+							m := s.RootModule()
+							i := m.Resources["data.local_exec.command"].Primary
+							if got, want := i.Attributes["stdout"], test.stdout; got != want {
+								return fmt.Errorf("stdout %q; want %q", got, want)
+							}
+							if got, want := i.Attributes["stderr"], test.stderr; got != want {
+								return fmt.Errorf("stderr %q; want %q", got, want)
+							}
+							if got, want := i.Attributes["rc"], test.rc; got != want {
+								return fmt.Errorf("rc %q; want %q", got, want)
+							}
+							return nil
+						},
+					},
+				},
+			})
+		})
+	}
+}

internal/provider/provider.go

@@ -11,6 +11,7 @@ func New() *schema.Provider {
 			"local_file": resourceLocalFile(),
 		},
 		DataSourcesMap: map[string]*schema.Resource{
+			"local_exec": dataSourceLocalExec(),
 			"local_file": dataSourceLocalFile(),
 		},
 	}

website/docs/d/exec.html.md

@@ -0,0 +1,52 @@
+---
+layout: "local"
+page_title: "Local: local_exec"
+sidebar_current: "docs-local-datasource-exec"
+description: |-
+  Executes a command on the local system and returns stdout, stderr and rc.
+---
+
+# local_exec
+
+`local_exec` executes a command on the local system.
+
+## Example Usage
+
+```hcl
+data "local_exec" "touch" {
+  command     = ["touch", "bar"]
+  working_dir = "/tmp"
+}
+
+data "local_exec" "sh" {
+  command        = ["sh", "-c", "echo hello world && curl -L https://google.com"]
+  ignore_failure = true
+}
+
+```
+
+## Argument Reference
+
+The following arguments are supported:
+
+* `command` - (Required) Command and arguments to execute. This is expected as
+  a list with the first element being the the binary to execute. The rest will
+  be passed as arguments to the binary on execution. The binary should be
+  available in the `PATH` or should be an absolute path.
+* `working_dir` - (Optional) The directory to change to before executing the
+  specified command. If unspecified, the process's current directory will be
+  used.
+* `ignore_failure` - (Optional) By default, any failures during the execution
+   of the command will cause an error in your Terraform execution. If an error
+   is expected or not fatal, this may be set to `true` to ignore any such
+   failures.
+
+## Attributes Exported
+
+The following attributes are exported:
+
+* `stdout` - The raw content of stdout of the process executing the command.
+* `stderr` - The raw content of stderr of the process executing the command.
+* `rc` - The exit code of the process executing the command. On success, this
+  is always 0. On failure, this retrieved at best effort and defaults to `-1`
+  if it cannot be retrieved.