| // Copyright 2021 Google LLC |
| // |
| // 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 sysapi |
| |
| import ( |
| "bytes" |
| "io/ioutil" |
| "os" |
| "os/exec" |
| "path/filepath" |
| "syscall" |
| ) |
| |
| // AtomicWriteFile atomically writes a file. |
| func AtomicWriteFile(name string, content []byte, perm os.FileMode) error { |
| |
| // Write to a temporary file in the same directory first. This is to |
| // guarantee the the temporary file and the intended file are on the |
| // same filesystem. |
| dir := filepath.Dir(name) |
| tmpFile, err := ioutil.TempFile(dir, "atom_write") |
| if err != nil { |
| return err |
| } |
| |
| // Write the file. os.Write() is guaranteed to return a non-nil error |
| // when the number of bytes written != len(content). |
| _, err = tmpFile.Write(content) |
| if err1 := tmpFile.Close(); err == nil { |
| err = err1 |
| } |
| if err != nil { |
| os.Remove(tmpFile.Name()) |
| return err |
| } |
| |
| // Rename the temporary file to the desired name. This is an atomic |
| // operation on POSIX compliant file systems. |
| return syscall.Rename(tmpFile.Name(), name) |
| } |
| |
| // RunCommand returns the stdout and stderr produced by running the named |
| // program with the given arguments. |
| func RunCommand(name string, args ...string) ([]byte, []byte, error) { |
| cmd := exec.Command(name, args...) |
| |
| var stdout, stderr bytes.Buffer |
| cmd.Stdout = &stdout |
| cmd.Stderr = &stderr |
| |
| if err := cmd.Run(); err != nil { |
| return nil, nil, err |
| } |
| |
| return stdout.Bytes(), stderr.Bytes(), nil |
| } |
| |
| // FileExists checks if the named file exists. |
| func FileExists(path string) bool { |
| if _, err := os.Stat(path); os.IsNotExist(err) { |
| return false |
| } |
| return true |
| } |