2025 8 15 https://shelter.sirref.org/parallel-for/ parallel-for /parallel-for/ Shelterfile Syntax › Parallel Loops Given Shelter's underlying mergeable structure, it can offer a rather unique model for parallel computation. Tools exist within the shell scripting world for taking scripts and arguments and running them in parallel. For example, GNU parallel or littlejohn. These tools, like Shelter, use processes for parallelism. Shelter, however, runs the processes in isolation using namespaces which gives us two advantages: It ensures that the parallel parts cannot interfere with one another. Each instantiation of the body of the loop starts from the same starting point Since each loop-body is independent, successful executions are recorded and do not need to be re-run in the event of a partial failure. After all parts of the loop have completed, the resulting data is merged and execution continues from there. By providing this as an extra feature, if users do not like these semantics, they can always opt to use a more generic tool for their parallelism too! 2025 8 15 Syntax For now, parallel for-loops are rather simplistic. #file }]]> You may introduce a variable, here file, which will take on the value in your referenced using # and will be replaced accordingly. References Context 2025 8 15 https://shelter.sirref.org/shelterfile-syntax/ shelterfile-syntax /shelterfile-syntax/ Shelterfile Syntax Shelterfiles, files with a .shl extension, are a funny mix of syntax borrowing from Dockerfiles and shell scripts. 2025 8 15 https://shelter.sirref.org/basix-syntax/ basix-syntax /basix-syntax/ Basic Syntax meta-commands Take the following Dockerfile for example: hello2.txt]]> In Shelter, this can be expressed very similarly. hello2.txt]]> We have had to use two meta-commands to achieve the same functionality. The first line creates a fresh session using the alpine base image. We then import a file from the local filesystem into our image. 2025 8 15 https://shelter.sirref.org/conditionals/ conditionals /conditionals/ Conditionals Unlike Dockerfiles, we have the possibility to introduce conditionals. Conditionals allow you to check a certain command exits with 0 and if so execute the first branch, otherwise execute the second branch. 2025 8 15 Syntax The synax is similar to many programming languages' implementation of if-then-else constructs. 2025 8 15 https://shelter.sirref.org/parallel-for/ parallel-for /parallel-for/ Parallel Loops Given Shelter's underlying mergeable structure, it can offer a rather unique model for parallel computation. Tools exist within the shell scripting world for taking scripts and arguments and running them in parallel. For example, GNU parallel or littlejohn. These tools, like Shelter, use processes for parallelism. Shelter, however, runs the processes in isolation using namespaces which gives us two advantages: It ensures that the parallel parts cannot interfere with one another. Each instantiation of the body of the loop starts from the same starting point Since each loop-body is independent, successful executions are recorded and do not need to be re-run in the event of a partial failure. After all parts of the loop have completed, the resulting data is merged and execution continues from there. By providing this as an extra feature, if users do not like these semantics, they can always opt to use a more generic tool for their parallelism too! 2025 8 15 Syntax For now, parallel for-loops are rather simplistic. #file }]]> You may introduce a variable, here file, which will take on the value in your referenced using # and will be replaced accordingly. Backlinks Related Contributions