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Bash empty array expansion with `set -u`
...4.4.
$ bash --version | head -n 1
GNU bash, version 4.4.19(1)-release (x86_64-pc-linux-gnu)
$ set -u
$ arr=()
$ echo "foo: '${arr[@]}'"
foo: ''
There is a conditional you can use inline to achieve what you want in older versions: Use ${arr[@]+"${arr[@]}"} instead of "${arr[@]}".
$ function ...
Web-scraping JavaScript page with Python
...:
import requests
from bs4 import BeautifulSoup
response = requests.get(my_url)
soup = BeautifulSoup(response.text)
soup.find(id="intro-text")
# Result:
<p id="intro-text">No javascript support</p>
Scraping with JS support:
from selenium import webdriver
driver = webdriver.PhantomJS(...
What kind of leaks does automatic reference counting in Objective-C not prevent or minimize?
...chain referring back to an earlier object.
It is for this reason that the __unsafe_unretained and __weak ownership qualifiers exist. The former will not retain any object it points to, but leaves open the possibility of that object going away and it pointing to bad memory, whereas the latter doesn...
C/C++ line number
...
You should use the preprocessor macro __LINE__ and __FILE__. They are predefined macros and part of the C/C++ standard. During preprocessing, they are replaced respectively by a constant string holding an integer representing the current line number and by the cu...
Can I access constants in settings.py from templates in Django?
..., frequently-used settings constants to the template such as settings.MEDIA_URL and some of the language settings if you use django's built in generic views or pass in a context instance keyword argument in the render_to_response shortcut function. Here's an example of each case:
from django.short...
Docker - how can I copy a file from an image to a host?
...
Actually, I use docker run --rm --entrypoint tar _image_ cC _img_directory_ . | tar xvC _host_directory_
– caligari
Nov 30 '17 at 11:04
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How do synchronized static methods work in Java and can I use it for loading Hibernate entities?
...ic methods, you can
class SomeClass {
private static final Object LOCK_1 = new Object() {};
private static final Object LOCK_2 = new Object() {};
static void foo() {
synchronized(LOCK_1) {...}
}
static void fee() {
synchronized(LOCK_1) {...}
}
static void...
C# Sortable collection which allows duplicate keys
...Format("{0}:{1}", tuple.Item1,tuple.Item2));
}
int expected_first = 1;
int expected_last = 3;
int first = list.First().Item1; //requires using System.Linq
int last = list.Last().Item1; //requires using System.Linq
Assert.AreEqual(expected_first, fi...
Shell脚本编程30分钟入门 - 更多技术 - 清泛网 - 专注C/C++及内核技术
Shell脚本编程30分钟入门linux_shell_30min_guides什么是Shell脚本示例看个例子吧：#! bin shcd ~mkdir shell_tutcd shell_tutfor ((i=0; i<10; i++)); do touch test_$i.txt...
什么是Shell脚本
示例
看个例子吧：
#!/bin/sh
cd ~
mkdir shell_tut
cd shell_tut
for (...
What's the scope of a variable initialized in an if statement?
...ked only at runtime -- that is, when you get to the print x statement. If __name__ didn't equal "__main__" then you would get an exception: NameError: name 'x' is not defined.
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