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I'm trying to open a file and I'd like to know if it doesn't exist to react. But the error
os.OpenFile(fName, os.O_WRONLY, 0600)
returns when the file does not exist is different than os.ErrNotExists
os.ErrNotExists -> "file does not exist"
err.(*os.PathError).Err -> "no such file or directory"
os.Stat also return the same error if the file is not there. Is there a predefined error I can compare to instead of having to do it by hand?
746
In order to check if a particular file exists inside a given directory in Golang, we can use the Stat() and the isNotExists() function that the os package of Go's standard library provides us with. The Stat() function is used to return the file info structure describing the file.
To write to files in Go, we use the os , ioutil , and fmt packages. The functions that we use typically return the number of bytes written and an error, if any.
The os. Stat function attempts to resolve the path relative to the root of your project directory. If a matching file or directory is not found, it will attempt to resolve the path relative to the contentDir . A leading path separator ( / ) is optional.
Stdout, also known as standard output, is the default file descriptor where a process can write output. In Unix-like operating systems, such as Linux, macOS X, and BSD, stdout is defined by the POSIX standard. Its default file descriptor number is 1.
Package os
func IsExist
func IsExist(err error) boolIsExist returns a boolean indicating whether the error is known to report that a file or directory already exists. It is satisfied by ErrExist as well as some syscall errors.
func IsNotExist
func IsNotExist(err error) boolIsNotExist returns a boolean indicating whether the error is known to report that a file or directory does not exist. It is satisfied by ErrNotExist as well as some syscall errors.
Use the os.IsNotExist function. For example,
package main
import (
"fmt"
"os"
)
func main() {
fname := "No File"
_, err := os.OpenFile(fname, os.O_WRONLY, 0600)
if err != nil {
if os.IsNotExist(err) {
fmt.Print("File Does Not Exist: ")
}
fmt.Println(err)
}
}
Output:
File Does Not Exist: open No File: No such file or directory
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