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util.go
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util.go
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// Copyright 2018 The Kubeflow 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.
// Package util provides various helper routines.
package util
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"math/rand"
"os"
"os/exec"
"strings"
"time"
log "github.com/sirupsen/logrus"
)
// Pformat returns a pretty format output of any value that can be marshaled to JSON.
func Pformat(value interface{}) string {
if s, ok := value.(string); ok {
return s
}
valueJSON, err := json.MarshalIndent(value, "", " ")
if err != nil {
log.Warningf("Couldn't pretty format %v, error: %v", value, err)
return fmt.Sprintf("%v", value)
}
return string(valueJSON)
}
// src is variable initialized with random value.
var src = rand.NewSource(time.Now().UnixNano())
const letterBytes = "0123456789abcdefghijklmnopqrstuvwxyz"
const (
letterIdxBits = 6 // 6 bits to represent a letter index
letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
letterIdxMax = 63 / letterIdxBits // # of letter indices fitting in 63 bits
)
// RandString generates a random string of the desired length.
//
// The string is DNS-1035 label compliant; i.e. its only alphanumeric lowercase.
// From: https://stackoverflow.com/questions/22892120/how-to-generate-a-random-string-of-a-fixed-length-in-golang
func RandString(n int) string {
b := make([]byte, n)
// A src.Int63() generates 63 random bits, enough for letterIdxMax characters!
for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
if remain == 0 {
cache, remain = src.Int63(), letterIdxMax
}
if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
b[i] = letterBytes[idx]
i--
}
cache >>= letterIdxBits
remain--
}
return string(b)
}
// Run a subprocess and return stdout
func Run(command []string, dir string, env []string) ([]byte, error) {
log.Infof("Execute command: %s", strings.Join(command, " "))
if len(command) == 0 {
return nil, errors.New("Command cannot be empty.")
}
name := command[0]
args := command[1:]
cmd := exec.Command(name, args...)
cmd.Env = append(os.Environ(), env...)
if dir != "" {
cmd.Dir = dir
}
var stdout, stderr bytes.Buffer
cmd.Stdout = &stdout
cmd.Stderr = &stderr
err := cmd.Run()
if err != nil {
log.Errorf("Command failed: %s", err)
log.Errorf("Subprocess error:\n%s", string(stderr.Bytes()))
log.Infof("Subprocess output:\n%s", string(stdout.Bytes()))
return nil, err
}
output := stdout.Bytes()
log.Infof("Subprocess output:\n%s", string(output))
return output, err
}