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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2016 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package osutil
import (
"fmt"
"os"
"strconv"
"strings"
)
// GetenvBool returns whether the given key may be considered "set" in the
// environment (i.e. it is set to one of "1", "true", etc).
//
// An optional second argument can be provided, which determines how to
// treat missing or unparsable values; default is to treat them as false.
func GetenvBool(key string, dflt ...bool) bool {
if val := strings.TrimSpace(os.Getenv(key)); val != "" {
if b, err := strconv.ParseBool(val); err == nil {
return b
}
}
if len(dflt) > 0 {
return dflt[0]
}
return false
}
// GetenvInt64 interprets the value of the given environment variable
// as an int64 and returns the corresponding value. The base can be
// implied via the prefix (0x for 16, 0 for 8; otherwise 10).
//
// An optional second argument can be provided, which determines how to
// treat missing or unparsable values; default is to treat them as 0.
func GetenvInt64(key string, dflt ...int64) int64 {
if val := strings.TrimSpace(os.Getenv(key)); val != "" {
if b, err := strconv.ParseInt(val, 0, 64); err == nil {
return b
}
}
if len(dflt) > 0 {
return dflt[0]
}
return 0
}
// EnvMap takes a list of "key=value" strings and transforms them into
// a map.
func EnvMap(env []string) map[string]string {
out := make(map[string]string, len(env))
for _, kv := range env {
l := strings.SplitN(kv, "=", 2)
if len(l) == 2 {
out[l[0]] = l[1]
}
}
return out
}
// SubstituteEnv takes a list of environment strings like:
// - K1=BAR
// - K2=$K1
// - K3=${K2}
// and substitutes them top-down from the given environment
// and from the os environment.
//
// Input strings that do not have the form "k=v" will be dropped
// from the output.
//
// The result will be a list of environment strings in the same
// order as the input.
func SubstituteEnv(env []string) []string {
envMap := map[string]string{}
out := make([]string, 0, len(env))
for _, s := range env {
l := strings.SplitN(s, "=", 2)
if len(l) < 2 {
continue
}
k := l[0]
v := l[1]
v = os.Expand(v, func(k string) string {
if s, ok := envMap[k]; ok {
return s
}
return os.Getenv(k)
})
out = append(out, fmt.Sprintf("%s=%s", k, v))
envMap[k] = v
}
return out
}
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