See here. Basically:
dpkg --list apt-cache showpkg packagename apt-get install packagename=version echo "packagename hold" | sudo dpkg --set-selections
How to downgrade a package in Debian using apt-get and apt-cache
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Category Archives: Programming
Administering PostgreSQL
So I found this article which said:
$ sudo -u postgres psql
postgres=> alter user postgres password 'apassword'; postgres=> create user your-user createdb createuser password 'passwd'; postgres=> create database your-db-name owner your-user; postgres=> \q
Note: to enable password logins for the ‘postgres’ admin account, edit: /etc/postgresql/9.4/main/pg_hba.conf and after this line:
local all postgres peer
Add this line:
local all postgres md5
How do I list all databases and tables using psql?
So I found this which said:
- \list or \l
- list all databases
- \dt
- list all tables in the current database
Converting a C++ std::string to char*
So it turns out there is a std::string->c_str function. Note: I’m pretty sure this char[] will be deleted when the std::string is deleted…
C++ PostgreSQL example
Just followed this tutorial on how to create a basic C++ app that talks to a PostgreSQL database…
Code Assistance for C++ in NetBeans: define __cplusplus
See here:
- Go to Tools->Options
- Select C/C++ menu
- Select Code Assistance tab
- Select C++ Compiler tab
- In Macro Definitions list view, locate __cplusplus and change its value from 199711L to 201103L
- Click OK button
Gallery of Processor Cache Effects, MMUs, CPUID, etc.
Found Gallery of Processor Cache Effects… also of interest CPU cache, Memory Management Unit, and CPUID on Wikipedia.
What every programmer should know about memory
Just stumbled upon What every programmer should know about memory:
C++ Virtual Destructors and Base Classes
I’ve been wondering what happens when a derived class defines a virtual destructor. What about its base destructors? Are they called? If so, when? I finally read the right paragraph in The C++ Programming Language (pg 70):
A virtual destructor is essential for an abstract class because an object of a derived class is usually manipulated through a pointer to a base class. Then, the virtual function call mechanism ensures that the proper destructor is called. That destructor then implicitly invokes the destructors of its bases and members.
Still not sure when the bases and members are destructed, presumably after the derived virtual destructor…
C++ nested classes
Am reading The C++ Programming Language, 4ed, by Bjarne Stroustrup and his sixteenth suggestion for Java programmers (pg 21) is:
A C++ nested class does not have access to an object of the enclosing class.
I didn’t know that!