csub

Command Substitution for the Windows Command Shell

Summary

Most Unix-like shells support a technique called command substitution: a way to use the output of one command in the middle of another command. The Windows standard shell (command prompt) lacks this ability, but the csub command provides a simple way to mock this for most situations.

Usage

csub <command> [<arguments>] [`<sub-command>`]
               [<arguments>] [`<sub-command>`] …

Description

In most shells, one can accomplish command substitution by quoting a command with backquotes like so:

> echo It's a fine day in `hostname`-land.
It's a fine day in mycomputer03-land.

In other shells, like Bash, you can also accomplish this by enclosing the command in $(…), like this:

> echo It's a fine day in $(hostname)-land.
It's a fine day in mycomputer03-land.

The csub command provides a way to do this in the Windows command shell — anything in the csub arguments between backquotes is executed and replaced with the output, like so:

C:\> csub echo It's a fine day in `hostname`-land.
It's a fine day in mycomputer03-land.

Limitations

csub cannot change the environment at the calling level

The csub command is executed inside its own context, so commands that would change the environment cannot change the environment of the caller. For example,

C:\qux\baz\frotz> csub cd `echo \qux`

C:\qux\baz\frotz>

In the above example, you'd like the current directory to be C:\qux after running the command. The csub command does change the directory, but only it its own environment; it does not change the environment at the calling level.

Building

This project uses the CMake build tool. CMake is a meta-build system that locates and uses your local development tools to build the project if possible.

To build, first install [CMake][https://cmake.org/]. Then go to the project root directory and run the following command:

cmake -B build

This will locate your installed development tools and configure your project build in the build/ directory. After that, whenever you want a new build, run this command:

cmake --build build

This will build a debug version of the project, located in build/Debug/. To build a release version, run

cmake --build build --config release

You can find the built release executable in build/Release/.

Installation

The built executable is csub.exe, and can be copied anywhere to your command path. There is no Windows installation required for this tool.

Steve Hollasch, steve@hollasch.net
https://github.com/hollasch/csub