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How to list running screen sessions?
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To list all of the screen sessions for a user, run the following command as that user:
screen -ls
To see all screen sessions on a specific machine you can do:
ls -laR /var/run/screen/
I get this on my machine:
gentle ~ # ls -l...
How to drop rows of Pandas DataFrame whose value in a certain column is NaN
...ta, including dropna(), is built into pandas explicitly. Aside from potentially improved performance over doing it manually, these functions also come with a variety of options which may be useful.
In [24]: df = pd.DataFrame(np.random.randn(10,3))
In [25]: df.iloc[::2,0] = np.nan; df.iloc[::4,1] ...
Look up all descendants of a class in Ruby
... @AmolPujari p ObjectSpace.each_object(Class) will print out all the classes. You can also get the descendants of any class you want by substutiting its name for self in the line of code in the method.
– BobRodes
Apr 3 '19 at 20:38
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git recover deleted file where no commit was made after the delete
...this in my config file
$ git config alias.unstage
reset HEAD
which I usually use to unstage stuff.
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Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign
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This problem is usually caused by one of the following
null values being returned for columns not set to AllowDBNull
duplicate rows being returned with the same primary key.
a mismatch in column definition (e.g. size of char fields) between t...
XPath: How to select nodes which have no attributes?
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//node[not(@*)]
That's the XPath to select all nodes named "node" in the document without any attributes.
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What is the difference between persist() and merge() in JPA and Hibernate?
...these
other entities are annotated with the
cascade=PERSIST or cascade=ALL
annotation element value or specified
with the equivalent XML descriptor
element.
If X is a removed entity,
it becomes managed.
If X is a
detached object, the
EntityExistsException may be thrown
when the...
What REALLY happens when you don't free after malloc?
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Just about every modern operating system will recover all the allocated memory space after a program exits. The only exception I can think of might be something like Palm OS where the program's static storage and runtime memory are pretty much the same thing, so not freeing mig...
Design patterns to avoid [closed]
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Patterns are complex
All design patterns should be used with care. In my opinion you should refactor towards patterns when there is a valid reason to do so instead of implementing a pattern right away. The general problem with using patterns is t...
Learning Ant path style
...hes com/test.jsp but also com/tast.jsp or com/txst.jsp
com/*.jsp - matches all .jsp files in the com directory
com/**/test.jsp - matches all test.jsp files underneath the com path
org/springframework/**/*.jsp - matches all .jsp files underneath the org/springframework path
org/**/servlet/bla.jsp - m...