英文:
Detecting whether something is on STDIN
问题
以下是要翻译的内容：
程序应该能够从终端的stdin获取输入，如下所示：
echo foobar | program
然而，在下面的程序源代码中，如果省略了管道，stdin读取将会阻塞：
package main
import (
"fmt"
"os"
)
func main() {
b := make([]byte, 1024)
r := os.Stdin
n, e := r.Read(b)
if e != nil {
fmt.Printf("Err: %s\n", e)
}
fmt.Printf("Res: %s (%d)\n", b, n)
}
那么，程序如何检测是否以这种方式将某些内容传递给它，并在没有传递内容时继续执行而不阻塞呢？
...这样做是个好主意吗？
英文:
Program should be able to get input from stdin on terminal, as follows:
echo foobar | program
However, in the source below for Program, the stdin read blocks if the pipe is omitted:
package main
import (
"fmt"
"os"
)
func main() {
b := make([]byte, 1024)
r := os.Stdin
n, e := r.Read(b)
if e != nil {
fmt.Printf("Err: %s\n", e)
}
fmt.Printf("Res: %s (%d)\n", b, n)
}
So how can Program detect whether something is being piped to it in this manner, and continue execution instead of blocking if not?
... and is it a good idea to do so?
答案1
得分: 1
os.Stdin 被视为文件并具有权限。当 os.Stdin 打开时，权限为 0600，当关闭时为 0620。
以下是代码的翻译：
package main
import (
"fmt"
"os"
)
func main() {
stat, _ := os.Stdin.Stat()
fmt.Printf("标准输入模式: %v\n", stat.Mode().Perm())
if stat.Mode().Perm() == 0600 {
fmt.Printf("标准输入已打开\n")
return
}
fmt.Printf("标准输入已关闭\n")
}
希望对你有帮助！
英文:
os.Stdin is treated like a file and has permissions. When os.Stdin is open, the perms are 0600, when closed it's 0620.
This code works:
package main
import (
"fmt"
"os"
)
func main() {
stat, _ := os.Stdin.Stat()
fmt.Printf("stdin mode: %v\n", stat.Mode().Perm())
if stat.Mode().Perm() == 0600 {
fmt.Printf("stdin open\n")
return
}
fmt.Printf("stdin close\n")
}
答案2
得分: 0
如果你将读取操作放在一个 goroutine 中，并在主函数中使用 select 进行非阻塞读取通道，那么这是可能的。但是这样会导致竞态条件，取决于数据是否足够快地到达，你可能会得到不同的结果。你试图解决的更大问题是什么？
英文:
It would be possible if you put the read in a goroutine and use select to do a non-blocking read from the channel in main, but you would then have a race condition where you could get different results depending on whether the data comes in quickly enough. What is the larger problem you're trying to solve?
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