---
layout: default
navsection: userguide
title: "Tutorial: Your first job"
navorder: 20
---

h1. Tutorial: Your first job

Here you will use the "arv" command line tool to run a simple Crunch script on some sample data.

h3. Prerequisites

* Log in to a VM "using SSH":ssh-access.html
* Put an "API token":api-tokens.html in your @ARVADOS_API_TOKEN@ environment variable
* Put the API host name in your @ARVADOS_API_HOST@ environment variable

If everything is set up correctly, the command @arv -h user current@ will display your account information.

Arv depends on a few gems. It will tell you which ones to install, if they are not present yet. If you need to install the dependencies and are doing so as a non-root user, make sure you set GEM_HOME before you run gem install:

<pre>
    export GEM_HOME=~/.gem
</pre>

h3. Submit a job

We will run the "hash" program, which computes the MD5 hash of each file in a collection.

Pick a data collection. We'll use @f815ec01d5d2f11cb12874ab2ed50daa@ here.

<pre>
the_collection=f815ec01d5d2f11cb12874ab2ed50daa
</pre>

Pick a code version. We'll use @cdde7f246fec59bc99da86145fd4cf4efcf37a68@ here.

<pre>
the_version=cdde7f246fec59bc99da86145fd4cf4efcf37a68
</pre>

Make a JSON object describing the job.

<pre>
read -rd "\000" the_job <<EOF
{
 "script":"hash",
 "script_version":"$the_version",
 "script_parameters":
 {
  "input":"$the_collection"
 }
}
EOF
</pre>

(The @read -rd "\000"@ stuff just helps us get a multi-line string with lots of double quotation marks into a shell variable.)

Submit the job.

<pre>
arv -h job create --job "$the_job"
</pre>

Go to Workbench, drop down the Compute menu, and click Jobs. The job you submitted should appear at the top of the list.

Hit "Refresh" until it finishes.

You can also watch the log messages while the job runs:

<pre>
curl -s -H "Authorization: OAuth2 $ARVADOS_API_TOKEN" \
  https://{{ site.arvados_api_host }}/arvados/v1/jobs/JOB_UUID_HERE/log_tail_follow
</pre>

Great. You ran a job!