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What is the difference between active and passive FTP?
...nd passive are the two modes that FTP can run in.
For background, FTP actually uses two channels between client and server, the command and data channels, which are actually separate TCP connections.
The command channel is for commands and responses while the data channel is for actually transferr...
What does !! mean in ruby?
...:
!!nil #=> false
!!"abc" #=> true
!!false #=> false
It's usually not necessary to use though since the only false values to Ruby are nil and false, so it's usually best to let that convention stand.
Think of it as
!(!some_val)
One thing that is it used for legitimately is preventi...
How to take backup of a single table in a MySQL database?
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SQL usually compresses well--you can pipe the command above through gzip and the resulting file will be much smaller: mysqldump db_name table_name | gzip > table_name.sql.gz to restore: gunzip < table_name.sql.gz | mysql -u...
Git commits are duplicated in the same branch after doing a rebase
...nario presented in Pro Git about The Perils of Rebasing . The author basically tells you how to avoid duplicated commits:
...
What is the best way to use a HashMap in C++?
...p the elements are sorted by the key, insert and access is in O(log n). Usually the standard library internally uses red black trees for ordered maps. But this is just an implementation detail. In an unordered map insert and access is in O(1). It is just another name for a hashtable.
An example wit...
How to send PUT, DELETE HTTP request in HttpURLConnection?
I want to know if it is possible to send PUT, DELETE request (practically) through java.net.HttpURLConnection to HTTP-based URL.
...
Git stash pop- needs merge, unable to refresh index
...hor did was:
julita@yulys:~/GNOME/baobab/help/C$ git reset --hard origin/mallard-documentation
HEAD is now at ff2e1e2 Add more steps for optional information for scanning.
I.e aborting the current merge completely, allowing the git stash pop to be applied.
See "Aborting a merge in Git".
Those ar...
Bash Script : what does #!/bin/bash mean? [duplicate]
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That is called a shebang, it tells the shell what program to interpret the script with, when executed.
In your example, the script is to be interpreted and run by the bash shell.
Some other example shebangs are:
(From Wikipedia)
#...
Unknown Column In Where Clause
...
If you're trying to perform a query like the following (find all the nodes with at least one attachment) where you've used a SELECT statement to create a new field which doesn't actually exist in the database, and try to use the alias for that result you'll run into the same problem:
...
Post-increment and pre-increment within a 'for' loop produce same output [duplicate]
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When increment is called for a class, it might become non-equal to call post- or pre- increment, since it's behavior might differ much.
– mbaitoff
Jan 16 '11 at 15:48
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