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Effects of the extern keyword on C functions
...since it will be encountered later. Functions and variables are treated equally in this regard.
It's very useful if you need to share some global between modules and don't want to put / initialize it in a header.
Technically, every function in a library public header is 'extern', however labeling...
What is the reason for performing a double fork when creating a daemon?
... by setsid(). So, the first forked process becomes a session leader after calling setsid() and then we fork again so that the final, double-forked process is no longer a session leader. Other than the requirement of setsid() to be a session leader, you are spot on.
– dbmikus
...
What's the difference between Invoke() and BeginInvoke()
...y, on a threadpool thread.
Control.Invoke: Executes on the UI thread, but calling thread waits for completion before continuing.
Control.BeginInvoke: Executes on the UI thread, and calling thread doesn't wait for completion.
Tim's answer mentions when you might want to use BeginInvoke - although i...
Why is XOR the default way to combine hashes?
...paper that explains that combining hashes securely where each function is called only once is not possible without outputting less bits than the sum of number of bits in each hash value. This suggest that this answer is not correct.
– Tamás Szelei
Jul 23 '12 a...
updating table rows in postgres using subquery
...
Postgres allows:
UPDATE dummy
SET customer=subquery.customer,
address=subquery.address,
partn=subquery.partn
FROM (SELECT address_id, customer, address, partn
FROM /* big hairy SQL */ ...) AS subquery
WHERE dummy.addre...
Linq to Entities join vs groupjoin
...groups. This can be turned into a flat list of parent-child pairs by two small additions:
from p in parents
join c in children on p.Id equals c.Id into g // <= into
from c in g.DefaultIfEmpty() // <= flattens the groups
select new { Parent = p.Value, Child = c?.ChildValue }
The ...
Which is generally best to use — StringComparison.OrdinalIgnoreCase or StringComparison.InvariantCul
...onsider using a new set of String overloads in Microsoft .NET 2.0. Specifically, data that is designed to be culture-agnostic and linguistically irrelevant should begin specifying overloads using either the StringComparison.Ordinal or StringComparison.OrdinalIgnoreCase members of the new StringCompa...
How can you diff two pipelines in Bash?
...dev/fd/63 to get a filename that the command can open and read from to actually read from an already-open file descriptor that bash set up before exec'ing the command. (i.e. bash uses pipe(2) before fork, and then dup2 to redirect from the output of quux to an input file descriptor for diff, on fd ...
What is the difference between CMD and ENTRYPOINT in a Dockerfile?
...ypoint. i.e., the actual thing that gets executed is /bin/sh -c bash. This allowed Docker to implement RUN quickly by relying on the shell's parser.
Later on, people asked to be able to customize this, so ENTRYPOINT and --entrypoint were introduced.
Everything after ubuntu in the example above is ...
Add unique constraint to combination of two columns
...ctive, PersonNumber)
VALUES(N'foo', 1, 22);
GO
Data in the table after all of this:
ID Name Active PersonNumber
---- ------ ------ ------------
1 foo 1 22
2 foo 0 22
Error message on the last insert:
Msg 2627, Level 14, State 1, Line 3
Violation of UNIQUE KEY c...