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What is pluginManagement in Maven's pom.xml?
...uginManagement is only a way to share the same plugin configuration across all your project modules.
From Maven documentation:
pluginManagement: is an element that is seen along side plugins. Plugin Management contains plugin elements in much the same way, except that rather than configuring pl...
mongoDB/mongoose: unique if not null
...ngoDB v1.8+ you can get the desired behavior of ensuring unique values but allowing multiple docs without the field by setting the sparse option to true when defining the index. As in:
email : {type: String, trim: true, index: true, unique: true, sparse: true}
Or in the shell:
db.users.ensureIn...
Is double square brackets [[ ]] preferable over single square brackets [ ] in Bash?
...
[[ has fewer surprises and is generally safer to use. But it is not portable - POSIX doesn't specify what it does and only some shells support it (beside bash, I heard ksh supports it too). For example, you can do
[[ -e $b ]]
to test whether a file exists....
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
...
Difference between const & const volatile
...mize or reorder access to the object.
In an embedded system, this is typically used to access hardware registers that can be read and are updated by the hardware, but make no sense to write to (or might be an error to write to).
An example might be the status register for a serial port. Various b...
What are the reasons why Map.get(Object key) is not (fully) generic
...ethod is possible to have a Map<ArrayList, Something> and for me to call get() with a LinkedList as argument, and it should retrieve the key which is a list with the same contents. This would not be possible if get() were generic and restricted its argument type.
...
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 does void* mean and how to use it?
...a pointer to a function that compares two elements of the array. It gets called like so:
int iArr[10];
double dArr[30];
long lArr[50];
...
qsort(iArr, sizeof iArr/sizeof iArr[0], sizeof iArr[0], compareInt);
qsort(dArr, sizeof dArr/sizeof dArr[0], sizeof dArr[0], compareDouble);
qsort(lArr, sizeof...
Detecting that the browser has no mouse and is touch-only
... not a good way to move forward (and it is somewhat inconsistent). Additionally, unless you are tracking a very specific event or only trying to rule out a few classes above, using events themselves isn't full proof.
For example, say you've discovered that a user have emitted a real mousemove (not ...
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...