# Job pipeline using slurm dependencies

Some times we need to launch a list of jobs that execute in sequence, one after another.
In those cases we will use the **--depency** **sbatch** option, check the manual page for more details, we will only present a simple example.

## Simple example

Suppose we need to submit the script ***my_first_job.sh*** and then ***mu_second_job.sh*** that should run after the first one:

	[user@cirrus01 ~]$ sbatch my_first_job.sh
    Submitted batch job 1843928

	[user@cirrus01 ~]$ sbatch --dependency=after:1843928 my_second_job.sh
    Submitted batch job 1843921
    
    [user@cirrus01 ~]$ squeue
    JOBID   PARTITION              NAME USER ST TIME NODES NODELIST(REASON) 
    1843928       hpc   my_first_job.sh user  R 0:11     1 hpc046
    1843921       hpc  my_second_job.sh user PD 0:00     1 hpc047

In this case the second job will run even if the first job fails for some reason. The pending job will execute when the first finish his execution.

## Tipical example

On a real case we may need the ensure that a good termination of the first job, for example, the first job may produce some output file needed as input for the second job:

	[user@cirrus01 ~]$ sbatch my_first_job.sh
    Submitted batch job 1843922

	[user@cirrus01 ~]$ sbatch --dependency=afterok:1843922 my_second_job.sh
    Submitted batch job 1843923

The ***afterok*** parameter states that the second job would start only if the previous job terminate with no errors.

## Complex cases

Check the ***sbatch*** manual page for more details:

	 [user@cirrus01 ~]$ man sbatch

search for the ***-d, --dependency=<dependency_list>*** options explanation.