如何使用settimeofday(2)? [英] how to use settimeofday(2)?

问题描述

我在这里做错了什么?我希望settimeofday()更改系统时间，而不返回EINVAL.

What am I doing wrong here? I expect settimeofday() to change the system time, not return EINVAL.

$ uname -a
Linux io 4.3.5-300.fc23.x86_64 #1 SMP Mon Feb 1 03:18:41 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
$ cat settimeofday.c 
#include <sys/time.h>
#include <stdio.h>

int main()
{
    struct timeval tv = {0, 0};
    if (settimeofday(&tv, 0) == -1)
        perror("settimeofday");
}
$ gcc settimeofday.c 
$ sudo ./a.out 
settimeofday: Invalid argument

该错误来自运行Fedora 23的Thinkpad T450.相同的代码在OS X上运行正常.

The error is coming from a Thinkpad T450 running Fedora 23. The same code runs fine on OS X.

编辑

为澄清起见，该命令以root用户身份执行:

To clarify, the command is being executed as root:

# whoami
root
# sudo ./a.out 
settimeofday: Invalid argument

按预期，如果我以常规用户身份运行程序，则会得到EPERM而不是EINVAL:

As expected, I get EPERM not EINVAL if I run the program as a regular user:

$ ./a.out 
settimeofday: Operation not permitted

推荐答案

提交 e1d7ba 于2015年中期引入Linux内核，并限制了tv_sec字段的值.该限制受系统正常运行时间的影响-有关详细信息，请参见提交消息和相关的LKML讨论.

Commit e1d7ba was introduced to the Linux kernel in mid-2015 and restricts the value of the tv_sec field. The restriction is influenced by system uptime -- see the commit message and related LKML discussion for details.

这就是导致settimeofday调用返回EINVAL的原因，并解释了为什么代码在OS X和较旧的Linux机器上运行.

That's what was causing the settimeofday call to return EINVAL and explains why the code runs on OS X and older Linux machines.

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