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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 (...
How to delete items from a dictionary while iterating over it?
...--------------------------------------------------
Traceback (most recent call last):
File "<ipython console>", line 1, in <module>
RuntimeError: dictionary changed size during iteration
As stated in delnan's answer, deleting entries causes problems when the iterator tries to move on...
Check if a value is an object in JavaScript
...o examine variable's properties, but it is not a bulletproof recipe (after all there's no recipe at all!) for checking whether it's an object, far from it. Since people tend to look for something to copy from here without doing any research, I'd highly recommend that they turn to the other, most upv...
Batch file include external file for variables
...eem to be unaware that there are significant differences and just blindly call everything with grey text on black background DOS. Nevertheless, the first variant should work in DOS as well.
Executable configuration
The easiest way to do this is to just put the variables in a batch file themselves, e...
Entity Framework 6 Code first Default value
...
You can do it by manually edit code first migration:
public override void Up()
{
AddColumn("dbo.Events", "Active", c => c.Boolean(nullable: false, defaultValue: true));
}
...
How to concatenate strings in twig
...like Alessandro said, and here it is in the documentation:
~: Converts all operands into strings and concatenates them. {{ "Hello
" ~ name ~ "!" }} would return (assuming name is 'John') Hello John!. – http://twig.sensiolabs.org/doc/templates.html#other-operators
And here is an example so...
indexOf method in an object array?
... think to see the performance of this method vs. a simple for loop. Especially when you're running on a mobile platform with limited resources.
– Doug
Aug 17 '15 at 5:51
...
How to check if object has any properties in JavaScript?
...d Apr 20 '10 at 6:49
Daniel VassalloDaniel Vassallo
301k6666 gold badges475475 silver badges424424 bronze badges
...
Difference between variable declaration syntaxes in Javascript (including global variables)?
...here are a couple of differences, though in practical terms they're not usually big ones.
There's a fourth way, and as of ES2015 (ES6) there's two more. I've added the fourth way at the end, but inserted the ES2015 ways after #1 (you'll see why), so we have:
var a = 0; // 1
let a = 0; // 1...
Extract a substring according to a pattern
... sub to replace it with a colon first. For example, if the separator were _ then string <- sub("_", ":", string)
c(read.dcf(textConnection(string)))
## [1] "E001" "E002" "E003"
7) separate
7a) Using tidyr::separate we create a data frame with two columns, one for the part before the colon and o...