Disclaimer: please stop telling me this is bad idea or bad implementation. I was just trying C++ filesystem API; had fun setting executable bit on a .cpp file; haven't yet created (and so far have no plans to create) any useful C++ scripts; uploaded it to github because was asked to; and was very surprised to get huge feedback, enhancement requests and even pull requests O_O for such a trivial next-to-hello-world program.

BTW, anyone needs remote Software Developer? Middle C++, or Senior Java / Scala / PHP / fullstack web. Resume: http://dimgel.me/en/Dmitry_Grigoriev_resume_en-short.pdf

1. Compile and install build-n-run.cpp: make && sudo make install.

2. Create C++ source file, prepend it with shebang line #!/usr/local/bin/build-n-run, make it executable chmod +x script.cpp and run: ./script.cpp. An example hello.cpp script is provided.

3. build-n-run compiles script.cpp to ~/.cache/build-n-run/ only if source file is newer than compiled binary, and then runs compiled binary.

They say compiled languages are inconvenient for scripting because you have to recompile your script everytime you edit it. A little program build-n-run.cpp presented in this repo solves the problem.

In bash scripts, first line always starts with "shebang" followed by name of a bash interpreter. When you run bash script, effectively bash interpreter is run and this script is passed to it as first argument.

    #!/bin/bash
    echo "Hello world!"

Same approach is used for Python scripts, Scala scripts, etc. So I did the same: example script hello.cpp in this repo is normal C++ program prepended with shebang line:

    #!/usr/local/bin/build-n-run
    #include <stdio.h>
    int main() {
        puts("Hello world!");
    }

build-n-run automatically recompiles script if it is new or edited (i.e. if compiled binary does not exist or if source file's modification time is newer than binary's) and then runs it:

    $ hello.cpp
    Recompiling...    <--- First time you run your script, it's recompiled.
    Hello world!

    $ hello.cpp
    Hello world!      <--- No recompilation on next run if script is unchanged.

1. Download build-n-run.cpp from this repo.

2. (Optional) Check its source code: you might want to update GCC options used to compile your scripts, or remove "Recompiling..." message if it messes with our scripts' output.

3. Build and install it. make install copies binary to /usr/local/bin; you can copy it anywhere you want, just don't forget to update path in scripts' shebang line. I use gcc 7.3.0, so I explicitly link libstdc++fs.a which implements std::experimental::filesystem.

    # make && sudo make install
   

That's all. Now write C++ program with shebang line, chmod it to be executable, and run:

    $ chmod +x hello.cpp
    $ ./hello.cpp
    Recompiling...
    Hello world!

Let's take a look at ~/.cache/build-n-run directory:

    $ ls ~/.cache/build-n-run
    home--me--tmp--hello

I downloaded hello.cpp to /home/me/tmp, and compiled binary's name reflects source's full path, slashes replaced with "--".

Compiled cache is inside user's home, so scripts compiled by one user cannot be run by other users (see issue #1).

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