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What is the best way to ensure only one instance of a Bash script is running? [duplicate]
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If the script is the same across all users, you can use a lockfile approach. If you acquire the lock, proceed else show a message and exit.
As an example:
[Terminal #1] $ lockfile -r 0 /tmp/the.lock
[Terminal #1] $
[Terminal #2] $ lockfile -r 0 /tmp/the....
How should one use std::optional?
...std::string s, int& i);
Another way that this could be done is especially bad:
int* try_parse_int(std::string s); //return nullptr if fail
This requires dynamic memory allocation, worrying about ownership, etc. - always prefer one of the other two signatures above.
Another example:
clas...
Python argparse: Make at least one argument required
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args = vars(parser.parse_args())
if not any(args.values()):
parser.error('No arguments provided.')
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str performance in python
...; import dis
>>> dis.dis(lambda: str(100000))
8 0 LOAD_GLOBAL 0 (str)
3 LOAD_CONST 1 (100000)
6 CALL_FUNCTION 1
9 RETURN_VALUE
>>> dis.dis(lambda: '%s' % 100000)
9 0 LOAD...
ASP.NET MVC 3 - Partial vs Display Template vs Editor Template
...ch template gets chosen to generate the UI for the model. They are also usually used for data models (i.e. models that represent rows in a database, etc)
On the other hand Partial is view-centric in that you are mostly concerned with choosing the correct partial view. The view doesn't necessarily n...
How to JSON serialize sets?
...s.
As shown in the json module docs, this conversion can be done automatically by a JSONEncoder and JSONDecoder, but then you would be giving up some other structure you might need (if you convert sets to a list, then you lose the ability to recover regular lists; if you convert sets to a dictionar...
Python group by
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Python's built-in itertools module actually has a groupby function , but for that the elements to be grouped must first be sorted such that the elements to be grouped are contiguous in the list:
from operator import itemgetter
sortkeyfn = itemgetter(1)
input = [(...
Setting Vim whitespace preferences by filetype
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@JamesMcMahon expandtab expands all tabs to spaces. sts (softtabstop) inserts spaces and tabs for indents: as many tabs as will fit in the indent based on the size of tabstop, and then spaces after that. Of course, if expandtab is on, all the tabs that get ...
How to specify data attributes in razor, e.g., data-externalid=“23151” on @this.Html.CheckBoxFor(…)
...heckBox",
data_externalid = "23521"
}
)
The _ will automatically be converted to - in the resulting markup:
<input type="checkbox" name="MyModel.MyBoolProperty" data-externalid="23521" class="myCheckBox" />
And that's true for all Html helpers taking a htmlAttributes anonymou...
@try - catch block in Objective-C
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All work perfectly :)
NSString *test = @"test";
unichar a;
int index = 5;
@try {
a = [test characterAtIndex:index];
}
@catch (NSException *exception) {
NSLog(@"%@", exception.reason);
NSLog(@"Char at in...