Exercise - Use Bash and grep to filter CLI output

  • 3 minutes

Until now, you've been running Bash commands on their own. Bash is extremely powerful when combined with other tools, so let's get some practice by using Bash to filter output from the Azure CLI.

  1. Let's say you want to see an up-to-date list of the VM sizes available in the westus region of Azure. You can do that with this command:

    az vm list-sizes --location westus --output table

  2. You should see a long list of VM types as an output. To narrow down this list to the VM sizes you're interested in, you can use grep, Linux's universal pattern-matching program. To find the "DS" sizes, popular for use in data science, use the following command:

    az vm list-sizes --location westus --output table | grep DS

    This pipes output from the az command to grep, which filters out lines that lack the "DS" string.

  3. That's still a lot of VMs. You know that DS V2 VMs are a more recent series. Let's adjust the grep command to use a more intricate regular expression:

    az vm list-sizes --location westus --output table | grep DS.*_v2

    This filters out lines that don't match the regular expression DS.*_v2. You might recognize some of the characters in that expression from our discussion of "wildcards" in an earlier unit. Regular expressions make great use of wildcards.

    Regular expressions are a topic for another module, but come in handy for Bash scripting.

Using Bash with other CLI commands makes the latter easier to work with. And because a sysadmin's work never ends, any tool that reduces the workload is welcome.