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what is the difference between ?:, ?! and ?= in regex?
...ng the pure regular expression. Perhaps I can but I would have to rely on callback functions.
– Y. Yoshii
May 16 '18 at 7:17
...
Display two files side by side
...es only 72 columns for its output, but it's relatively easy to make it use all available columns of your terminal window:
pr -w $COLUMNS -m -t one.txt two.txt
Most shell's will store (and update) your terminal's screenwidth in the $COLUMNS environment variable, so we're just passing that value on...
Is it possible only to declare a variable without assigning any value in Python?
...ython is dynamic, so you don't need to declare things; they exist automatically in the first scope where they're assigned. So, all you need is a regular old assignment statement as above.
This is nice, because you'll never end up with an uninitialized variable. But be careful -- this doesn't mean...
How do you check that a number is NaN in JavaScript?
... in specs tc39.github.io/ecma262/#sec-isnan-number
– allsyed
Jul 11 '16 at 5:43
5
isNaN(parseFloa...
Swift - class method which must be overridden by subclass
...:
class MyVirtual {
// 'Implementation' provided by subclass
let fooImpl: (() -> String)
// Delegates to 'implementation' provided by subclass
func foo() -> String {
return fooImpl()
}
init(fooImpl: (() -> String)) {
self.fooImpl = fooImpl
}
}...
How to go to each directory and execute a command?
...oesn't match anything else than numbers, but in the general case, you basically always want to put the directory name in double quotes inside the loop. cd "$d" would be better in that it transfers to situations where the wildcard does match files whose names contain whitespace and/or shell metachar...
How do you use script variables in psql?
...ingle quotes in the SQL statement.
Thus this doesn't work:
SELECT * FROM foo WHERE bar = ':myvariable'
To expand to a string literal in a SQL statement, you have to include the quotes in the variable set. However, the variable value already has to be enclosed in quotes, which means that you need ...
How can I parse a YAML file in Python
...d without relying on C headers is PyYaml (documentation), which can be installed via pip install pyyaml:
#!/usr/bin/env python
import yaml
with open("example.yaml", 'r') as stream:
try:
print(yaml.safe_load(stream))
except yaml.YAMLError as exc:
print(exc)
And that's it. A...
What is array to pointer decay?
... decay doesn't happen.
If you're passing an array by value, what you're really doing is copying a pointer - a pointer to the array's first element is copied to the parameter (whose type should also be a pointer the array element's type). This works due to array's decaying nature; once decayed, size...
How to use multiple arguments for awk with a shebang (i.e. #!)?
...k treated that as a command and printed out every line of input unconditionally. That is why I put in the arbitrary_long_name==0 - it's supposed to fail all the time. You could replace it with some gibberish string. Basically, I was looking for a false-condition in awk that would not adversely affec...