WIP Add page on Slurm environment variables

doc.zih.tu-dresden.de/docs/jobs_and_resources/slurm_env_vars.md

+ Slurm Environment Variables
+
+* Following is restricted to `sbatch` command
+* Differentiation between input and output variables
+
+The Slurm controller will set variables in the environment of the batch script
+
+## Input Environment Variables
+
+Upon startup, `sbatch` will read and handle the options set in the so-called *input environment
+variables*. With few exceptions, all input variables will be set the same way as the corresponding
+commandline options and `#SBATCH` directives. The following table provides some input environment
+variables and the equivalent option to `sbatch`.
+For a comprehensive documentation, please visit Slurm's
+[page on input variables for sbatch](https://slurm.schedmd.com/sbatch.html#SECTION_INPUT-ENVIRONMENT-VARIABLES)
+. Here, you will find the entire list of input variables for the latest Slurm version. ZIH systems
+might operate on a older Slurm version.
+
+| Environment Variable          | Equivalent Option  |
+|:------------------------------|:-------------------|
+| `SBATCH_ACCOUNT`              | `-A, --account`    |
+| `SBATCH_CONSTRAINT`           | `-C, --constraint` |
+| `SBATCH_ERROR`                | `-e, --error`      |
+| `SBATCH_OUPUT`                | `-o, --output`     |
+| `SBATCH_JOB_NAME`             | `-J, --job-name`   |
+| `SBATCH_HINT` or `SLURM_HINT` | `--hint`           |
+| `SBATCH_MEM_BIN`              | `--mem-bind`       |
+
+!!! note "Priority: Commandline option > env. variable > option in jobfile"
+
+    Environment variables will override any options set in a batch script, and command line options
+    will override any environment variables.
+
+## Output Environment Variables
+
+The Slurm controller will set a number of *output environment variables* in the environment of the
+batch script. This allows to obtain values of Slurm parameters within the environment of the job
+script, e.g., `SLURM_JOB_ID`, `SLURM_NTASKS`, `SLURM_CPUS_PER_TASK`, `SLURM_MEM_PER_NODE`,
+`SLURM_JOB_NODELIST`, `SLURM_JOB_NUM_NODES` and many more, which is quite useful for automation and
+generalisation of job scripts.
+
+!!! example ""
+
+    The following skeleton of a job script for an OpenMP-parallel application depicts the
+    generalization w.r.t. setting the number of threads basing on the environment variable
+    `SLURM_CPUS_PER_TASKS`. By this, you can only have to adjust the number of cpus per tasks within
+    the SBATCH directive and the OpenMP environment variable will set to the right value
+    automatically.
+
+    ```console
+    #!/bin/bash
+
+    #SBATCH --cpus-per-task=4
+    [...]
+
+    if [ ! -z "${SLURM_CPUS_PER_TASK}" ] ; then
+      export OMP_NUM_THREADS=${SLURM_CPUS_PER_TASK}
+    else
+      export OMP_NUM_THREADS=1
+    fi
+    ```
+
+## Exporting Environment Variables to Slurm Jobs
+
+WIP:
+
+Using the `--export` option, you can export variables to the Slurm job at submit time.
+
+<!--https://slurm.schedmd.com/sbatch.html#OPT_export_4-->

doc.zih.tu-dresden.de/mkdocs.yml

@@ -114,6 +114,7 @@ nav:
       - Batch System Slurm: jobs_and_resources/slurm.md
       - Job Examples: jobs_and_resources/slurm_examples.md
       - Slurm Resource Limits: jobs_and_resources/slurm_limits.md
+      - Slurm Environment Variables: jobs_and_resources/slurm_env_vars.md
       - Slurm Job File Generator: jobs_and_resources/slurm_generator.md
       - Checkpoint/Restart: jobs_and_resources/checkpoint_restart.md
       - Binding and Distribution of Tasks: jobs_and_resources/binding_and_distribution_of_tasks.md