英文:
How to process stderr in go?
问题
我有一个名为"myapp"的应用程序。该应用程序只是将内容写入stderr。
重要的部分是，我想要捕获stderr中写入的内容，并实时处理它。我该如何做到这一点？
我尝试了下面的代码：
cmd := exec.Command("myapp") // 这个应用程序将内容打印到stderr
stderr, err := cmd.StderrPipe()
if err != nil {
log.Fatal(err)
}
if err := cmd.Start(); err != nil {
log.Fatal(err)
}
if b, err := ioutil.ReadAll(stderr); err == nil {
log.Println(string(b))
}
if err := cmd.Wait(); err != nil {
log.Fatal(err)
}
这段代码没有输出任何内容。我怀疑这是因为ioutil.ReadAll()不是正确的函数调用，因为它会等待EOF。我应该如何从stderr管道中读取内容？
你可以将执行的命令替换为任何输出到stdout或stderr的命令，比如tail -f mylogfile。关键是，我想要在内容写入stdout时进行处理。
英文:
I have an app called "myapp". That app simply writes to stderr.
The important bit is, I want to capture what is written in stderr and process it in real-time. How would I go about doing that?
I tried the code below. :
cmd := exec.Command("myapp") // this app prints lines to stderr
stderr, err := cmd.StderrPipe()
if err != nil {
log.Fatal(err)
}
if err := cmd.Start(); err != nil {
log.Fatal(err)
}
if b, err := ioutil.ReadAll(stderr); err == nil {
log.Println(string(b))
}
if err := cmd.Wait(); err != nil {
log.Fatal(err)
}
The code doesn't print out anyting. I suspect it's because ioutil.ReadAll() is not the proper func to call since it waits for EOF. How else would I read from the stderr pipe?
You can replace the command executed with anything that outputs to stdout or stderr like tail -f mylogfile. The point is, I want to process the lines as they are written to stdout.
答案1
得分: 4
StderrPipe返回一个ReadCloser。你可以使用它来创建一个bufio.Scanner，然后逐行读取：
sc := bufio.NewScanner(stderr)
for sc.Scan() {
fmt.Printf("Line: %s\n", sc.Text())
}
英文:
StderrPipe returns a ReadCloser. You can use that to create a bufio.Scanner and then read lines one by one:
sc := bufio.NewScanner(stderr)
for sc.Scan() {
fmt.Printf("Line: %s\n", sc.Text());
}
答案2
得分: 1
创建一个实现io.Writer接口的类型，并将其设置为command的stderr写入器。
type Processor struct{}
func (Processor) Write(b []byte) (int, error) {
// 在这里拦截数据
return os.Stdout.Write(b)
}
func main() {
cmd := exec.Command("mycommand")
cmd.Stderr = Processor{}
_ = cmd.Run()
}
英文:
Create a type that implements io.Writer and set that as the command's stderr writer.
type Processor struct{}
func (Processor) Write(b []byte) (int, error) {
// intercept data here
return os.Stdout.Write(b)
}
func main() {
cmd := exec.Command("mycommand")
cmd.Stderr = Processor{}
_ = cmd.Run()
}
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