I want to share a programming reference website that does a great job at listing programming constructs and commands for the most popular programming languages: http://hyperpolyglot.org/

What I really like about this site is it displays how to do something in similar languages in a side-by-side format. For example, it groups together the family of interpreted languages (Perl, Python, PHP, Ruby: http://hyperpolyglot.org/scripting). If you want to see how to perform something like a square root function, it displays the function names to use and what modules are necessary for import. If you want to see what the syntax difference in a for loop between languages, this will show that as well.

Some of the groups they have listed are:

• Interpreted languages (Perl, PHP, Python, Ruby)
• C++ style languages (C++, Objective C, Java, C#)
• Relational data languages (SQL, Awk, Pig)
• Numerical analysis software (MATLAB, R, NumPy)

They also have pages for programming tools as well:

• Unix shells (Bash, Dash, Ksh, Tcsh, Zsh)
• Text mode editors (Vim, Emacs, Nano)
• Version control (Git, SVN, CVS)
• Multiplexers (Screen, Tmux)