feat: add pg_config interface

pkg/env/doc.go

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+/*
+Copyright The CloudNativePG Contributors
+
+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.
+*/
+
+// Package env contains useful functions to manage the system environment
+package env

pkg/env/env.go

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+/*
+Copyright The CloudNativePG Contributors
+
+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.
+*/
+
+package env
+
+import "os"
+
+// GetOrDefault gets the value of an environment variable or the
+// passed default value.
+func GetOrDefault(env, def string) string {
+	if value, ok := os.LookupEnv(env); ok {
+		return value
+	}
+	return def
+}

pkg/postgres/pgconfig/doc.go

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+/*
+Copyright The CloudNativePG Contributors
+
+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.
+*/
+
+// Package pgconfig contains a Go interface for the "pg_config" utility
+package pgconfig

pkg/postgres/pgconfig/pgconfig.go

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+/*
+Copyright The CloudNativePG Contributors
+
+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.
+*/
+
+package pgconfig
+
+import (
+	"fmt"
+	"os/exec"
+	"strings"
+)
+
+// ConfigurationParameter represents a PostgreSQL configuration parameter name
+type ConfigurationParameter string
+
+const (
+	// BinDir is the location user executables. Use this, for example,
+	// to find the psql program. This is normally also the location
+	// where the pg_config program resides.
+	BinDir ConfigurationParameter = "bindir"
+
+	// PkgLibDir is the location of dynamically loadable modules, or
+	// where the server would search for them. (Other
+	// architecture-dependent data files might also be installed in
+	// this directory.)
+	PkgLibDir ConfigurationParameter = "pkglibdir"
+
+	// ShareDir is the location of architecture-independent support
+	// files.
+	ShareDir ConfigurationParameter = "sharedir"
+)
+
+// GetCondifurationParameter retrieves a PostgreSQL installation configuration parameter
+func GetCondifurationParameter(pgConfigBinary string, parameter ConfigurationParameter) (string, error) {
+	out, err := exec.Command(pgConfigBinary, "--"+string(parameter)).Output() //nolint:gosec
+	if err != nil {
+		return "", fmt.Errorf("failed to get the %q parameter from pg_config: %w", parameter, err)
+	}
+	return strings.TrimSpace(string(out)), nil
+}