这是一个foo.c将数据写入共享内存的程序.
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <stdint.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/shm.h>
int main()
{
key_t key;
int shmid;
char *mem;
if ((key = ftok("ftok", 0)) == -1) {
perror("ftok");
return 1;
}
if ((shmid = shmget(key, 100, 0600 | IPC_CREAT)) == -1) {
perror("shmget");
return 1;
}
printf("key: 0x%x; shmid: %d\n", key, shmid);
if ((mem = shmat(shmid, NULL, 0)) == (void *) -1) {
perror("shmat");
return 1;
}
sprintf(mem, "hello");
sleep(10);
sprintf(mem, …我试图找出C++标准是否指定了各种类型的大小之间的关系.例如,https : //stackoverflow.com/a/589599/1175080上的答案似乎声称:
sizeof(short int) <= sizeof(int) <= sizeof(long int)
/sf/answers/41277911/的另一个答案有类似的说法:
sizeof(int) <= sizeof(long)
我正在经历n3337.pdf(我相信C + 11标准的良好代理)但我找不到保证这些不等式的特定语言.
在n1256(C99)中,我可以在第5.2.4.2.1节中找到特定语言.整数类型的大小清楚地说明了每种类型的最小值和最大值,这些值间接地建立了大小之间的相对排序.
这些不等式是否在C++标准中类似地定义,还是直接从C继承？标准中的语言在哪里？
我的 中有以下两个依赖项requirements.txt：
$ pip3 install elasticsearch==7.0.0 requests==2.21.0
Collecting elasticsearch==7.0.0
Using cached https://files.pythonhosted.org/packages/a8/27/d3a9ecd9f8f972d99da98672d4766b9f62ef64c323c40bb5e2557e538ea3/elasticsearch-7.0.0-py2.py3-none-any.whl
Collecting requests==2.21.0
Using cached https://files.pythonhosted.org/packages/7d/e3/20f3d364d6c8e5d2353c72a67778eb189176f08e873c9900e10c0287b84b/requests-2.21.0-py2.py3-none-any.whl
Collecting urllib3>=1.21.1 (from elasticsearch==7.0.0)
Using cached https://files.pythonhosted.org/packages/39/ec/d93dfc69617a028915df914339ef66936ea976ef24fa62940fd86ba0326e/urllib3-1.25.2-py2.py3-none-any.whl
Collecting certifi>=2017.4.17 (from requests==2.21.0)
Using cached https://files.pythonhosted.org/packages/60/75/f692a584e85b7eaba0e03827b3d51f45f571c2e793dd731e598828d380aa/certifi-2019.3.9-py2.py3-none-any.whl
Collecting chardet<3.1.0,>=3.0.2 (from requests==2.21.0)
Using cached https://files.pythonhosted.org/packages/bc/a9/01ffebfb562e4274b6487b4bb1ddec7ca55ec7510b22e4c51f14098443b8/chardet-3.0.4-py2.py3-none-any.whl
Collecting idna<2.9,>=2.5 (from requests==2.21.0)
Using cached https://files.pythonhosted.org/packages/14/2c/cd551d81dbe15200be1cf41cd03869a46fe7226e7450af7a6545bfc474c9/idna-2.8-py2.py3-none-any.whl
requests 2.21.0 has requirement urllib3<1.25,>=1.21.1, but you'll have urllib3 1.25.2 which is incompatible.
Installing collected packages: urllib3, elasticsearch, certifi, chardet, idna, requests
Successfully installed certifi-2019.3.9 chardet-3.0.4 elasticsearch-7.0.0 idna-2.8 requests-2.21.0 urllib3-1.25.2
我想了解上面输出中出现的这个警告：
requests 2.21.0 …我的代码：
package main
import (
"fmt"
)
func main() {
a := [10]int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
b := a[1:4]
fmt.Println("a:", a)
fmt.Println("b:", b)
// Works fine even though c is indexing past the end of b.
c := b[4:7]
fmt.Println("c:", c)
// This fails with panic: runtime error: index out of range [4] with length 3
// d := b[4]
}
输出：
a: [0 1 2 3 4 5 6 7 8 9]
b: …可能重复:
检测DOM元素的内联/块类型
在走HTML5 DOM树时,我想确定每个元素是块级元素还是内联元素.
var divElement = document.getElementById('foo');
alert(divElement.style.display)
alert(window.getComputedStyle(divElement, null).getPropertyValue('display'))
我看到第一个警告显示空字符串,而第二个警告显示"阻止",所以我认为第二个技术是我需要使用的.这是一个jsfiddle:http://jsfiddle.net/UaFpv/
我想知道是否有任何缺点用window.getComputedStyle(divElement, null).getPropertyValue('display')做我的工作,比如跨浏览器的兼容性问题,等有没有可以解决这个问题的任何其他技术？
这是我的 C++ 代码：
#include <iostream>
#include <windows.h>
HHOOK hook;
LRESULT CALLBACK keyboardHook(int nCode, WPARAM wParam, LPARAM lParam)
{
std::cout << "Hook callback" << std::endl;
return CallNextHookEx(hook, nCode, wParam, lParam);
}
int main(int argc, char **argv)
{
hook = SetWindowsHookEx(WH_KEYBOARD, keyboardHook, NULL, NULL);
if (hook == NULL) {
std::cout << "Error " << GetLastError() << std::endl;
return 1;
}
std::cout << "Hook set" << std::endl;
}
我使用 Visual Studio 编译它，如下所示：
cl /D_WIN32_WINNT=0x0401 foo.cc /link user32.lib
当我运行它时，我收到错误 1428。
C:\>foo.exe
Error 1428
这就是错误1428的含义。 …
为什么以下Python语句会返回None？
>>> re.match('\b\w+\b', 'foo')
>>>
据我了解,这应该与单词相符foo.第一个\b应匹配单词的开头foo,\w+应匹配单词foo,最后\b应匹配单词的结尾foo.我的理解有什么问题？
比较变量是否包含我想要的可调用对象的正确方法是什么？我应该使用is运算符还是==运算符？
在下面的交互式会话中，我定义了两个可调用对象，f和g。我将一个分配给变量a，另一个分配给变量b。
现在，当我想检查是否a相同时f，两者a == f都a is f可以工作。
>>> def f():
... pass
...
>>> def g():
... pass
...
>>> a = f
>>> b = g
>>> a == f
True
>>> a is f
True
>>> a == g
False
>>> a is g
False
>>> b == f
False
>>> b is f
False
>>> b == …我有一个类似于以下的应用程序代码.
# Filename: app.py
class Foo:
def __init__(self):
self.callback = None
def set_handler(self, callback):
self.callback = callback
def run(self, details):
name, age = details.split('/')
if age.isdigit():
age = int(age)
else:
age = -1
return self.callback(name, age)
如您所见,它提供了set_handler一种设置回调的方法.稍后必须使用两个参数调用回调:字符串和整数.我试图在单元测试中确保这一点.
# Filename: test_app.py
import unittest
from app import Foo
class AppTest(unittest.TestCase):
def f(self, a, b):
# This callback should get called with the first argument as
# string and the second argument as integer
return repr(a) + ',' + repr(b)
def …我正在使用 bash。
$ bash --version
GNU bash, version 4.3.11(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
From `help read`
这就是前几行所说的help read：
$ help read | head
read: read [-ers] [-a array] [-d delim] [-i text] [-n nchars] [-N nchars] [-p prompt] [-t timeout] [-u fd] [name …