英文:
Why don't I see fmt logs in my terminal when running go app locally?
问题
我正在尝试调试我的 Golang 应用程序。目前，我有一个 API 请求不起作用，其中有这行代码：
fmt.Errorf("Object(%q).CopierFrom(%q).Run: %v", dstName, object, err)
我该如何查看这个错误日志的输出？如果不可能的话，还有其他一些调试 Golang 的方法吗？（最好是运行时调用）
英文:
I'm trying to debug my golang app. Currently, I have an API request that isn't working which has this line of code:
fmt.Errorf("Object(%q).CopierFrom(%q).Run: %v", dstName, object, err)
How can I view the output of this error log? And if it's not possible what are some other ways to debug in go? (runtime invocation would be nice)
答案1
得分: 2
fmt.Errorf创建一个error对象；它不会打印输出。
根据fmt.Errorf的文档：
func Errorf(format string, a ...interface{}) error
如果你只是想将消息打印到标准输出：
fmt.Printf("Object(%q).CopierFrom(%q).Run: %v\n", dstName, object, err)
如果你想写入错误日志，我建议查看log包。例如，如果你想写入标准错误：
logger := log.New(os.Stderr, "my-app", 0)logger.Printf("Object(%q).CopierFrom(%q).Run: %v", dstName, object, err)
英文:
fmt.Errorf creates an error object; it does not print.
From the docs for fmt.Errorf:
func Errorf(format string, a ...interface{}) error
If you're just trying to print the message to stdout:
fmt.Printf("Object(%q).CopierFrom(%q).Run: %v\n", dstName, object, err)
If you want to write to an error log, I recommend looking at the log package. For example, if you were looking to write to stderr:
logger := log.New(os.Stderr, "my-app", 0)logger.Printf("Object(%q).CopierFrom(%q).Run: %v", dstName, object, err)
答案2
得分: 2
fmt.Errorf()创建一个错误对象，但不会打印。如果你只是想将消息打印到标准输出，可以使用以下代码：
package mainimport ("fmt")func main() {const name, id = "bueller", 17err := fmt.Errorf("user %q (id %d) not found", name, id)fmt.Println(err.Error())}
输出结果为：
user "bueller" (id 17) not found
如果你想调试 Golang 代码，我推荐使用日志包，例如 zerolog：
package mainimport ("errors""github.com/rs/zerolog""github.com/rs/zerolog/log")func main() {// UNIX 时间比大多数时间戳更快且更小zerolog.TimeFieldFormat = zerolog.TimeFormatUnixerr := errors.New("seems we have an error here")log.Error().Err(err).Msg("this is an error")}
输出结果为：
{"level":"error","error":"seems we have an error here","time":1640795128,"message":"this is an error"}
英文:
fmt.Errorf() creates an error object. but not print.doc
If you're just trying to print the message to stdout:
run
package mainimport ("fmt")func main() {const name, id = "bueller", 17err := fmt.Errorf("user %q (id %d) not found", name, id)fmt.Println(err.Error())}
out:
user "bueller" (id 17) not found
if you want debug golang code, I recommend use log packages for example:
zerolog
package mainimport ("errors""github.com/rs/zerolog""github.com/rs/zerolog/log")func main() {// UNIX Time is faster and smaller than most timestampszerolog.TimeFieldFormat = zerolog.TimeFormatUnixerr := errors.New("seems we have an error here")log.Error().Err(err).Msg("this is an error")}
out:
{"level":"error","error":"seems we have an error here","time":1640795128,"message":"this is an error"}
答案3
得分: 1
fmt.Errorf创建一个错误，非常适合用于函数返回，但它不会自动记录日志。
如果你想简单地记录一个错误：
log.Printf("api X: error %v", err)
英文:
fmt.Errorf creates an error - ideal for function returns - but it's not implicitly logged.
If you want to log an error simply:
log.Printf("api X: error %v", err)
答案4
得分: 0
在使用任何函数之前，最好先阅读函数签名和注释。
// Errorf 根据格式说明符进行格式化，并将字符串作为满足 error 接口的值返回。//// 如果格式说明符包含带有 error 操作数的 %w 动词，// 返回的错误将实现一个返回该操作数的 Unwrap 方法。包含多个 %w 动词或者提供不实现 error 接口的操作数都是无效的。否则，%w 动词是 %v 的同义词。func Errorf(format string, a ...interface{}) error
英文:
It is better to read the function signature and comments before you use any functions.
// Errorf formats according to a format specifier and returns the string as a// value that satisfies error.//// If the format specifier includes a %w verb with an error operand,// the returned error will implement an Unwrap method returning the operand. It is// invalid to include more than one %w verb or to supply it with an operand// that does not implement the error interface. The %w verb is otherwise// a synonym for %v.func Errorf(format string, a ...interface{}) error
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