nix-shell workshop

cpp program with custom library

the example features a self made library called mylib which is packaged using nix - see mylib.nix and default.nix how that is done.

the library mylib is used in a program called main.

how to build: enter environment by typing nix-shell in ./c-programs afterwards change directory cd main and run make

finally run ./main to see the ultimate answer:

./main 
hello world from the #cccamp2015, the answer is 
42

go programs

this example features a minimal webserver. It shows a "Hello World" html page on port 8080. To start the Server run:

cd goexample
nix-shell    
go run helloworld.go

qt program

this example features a qt5 console application console:

run cd qt-program and nix-shell to get a qt5 including environment. afterwards run qmake and make to generate the console binary. finally run ./console to obtain:

hello beautiful world, from #cccamp2015! 

perl

python

enter environment by typing nix-shell in ./python-program run simpleCurl by running python simpleCurl http://test.de it will output the html of http://test.de

questions

• pick 3 of the examples above and build the software as described using nix-shell and run the programs to see that they work
• use nix-shell -p clang (instead of using nix-shell with default.nix) and compile the cpp program+library example using llvm instead of gcc
• when you compile the cpp program with custom library, can you still run the program from a different environment where you don't use nix-shell prior execution? also try this for the python example above and compare the results!
• what is the effect of running nix-shell --pure in one shell vs. running nix-shell in a second shell? use the export command in either to see what parameters changed. use https://www.diffchecker.com/diff to compare the values you obtained
• issue nix-env -qaP | grep python and see that there is python 2.x and 3.x ;figure out how to get a nix-shell with python 2.x and one with python 3.x, issue python --version to verify that you got the right version!
• nix-shell can be used with a local checkout of nixpkgs, nix-shell -I nixpkgs=/foo/bar/nixpkgs --pure -p cmake, therefore clone nixpkgs 'master' from https://github.com/nixos/nixpkgs and issue the above command. compare the result to nix-shell -I nixpkgs=/foo/bar/nixpkgs --pure -p cmake in regards to amount of downloads/ build targets and compare the two outcomes
• what is the major difference between using nix-shell and myEnvFun, read http://blog.lastlog.de/posts/developing_software_using_nixos/ to learn about myEnvFun. afterwards adapt the cpp program with custom library to use myEnvFun instead of nix-shell
• play with persistent nix-shell environments, see https://nixos.org/wiki/Development_Environments#Making_a_Persistent_nix-shell_Environment

documentation

• https://nixos.org/wiki/Development_Environments
• http://blog.lastlog.de/posts/developing_software_using_nixos/