Today I realized that I’d left out setting the content type on a bunch of blobs that I uploaded over a number of days. My first thought was just to multi-select blobs in Azure Storage Explorer and be done with it, but alas it doesn’t allow batch updates. It looked more and more like I’d be forced to dvelve into Powershell to fix it - the horror!

Fortunately it turned out that the Azure CLI tool combined with the usual Unix toolbelt is flexible enough to get me out of this bind all by itself.

First set the connection string in an environment variable so you don’t have to keep wielding it around.

% az login
% export AZURE_STORAGE_CONNECTION_STRING=$(az storage account show-connection-string -g <resource-group> -n <storage-account> --output tsv)

Then the monster

% az storage blob list -c <container-name> --prefix <prefix> -o tsv \
 | awk '{print $3}' \
 | grep "\.jpg"\
 | xargs -n1 az storage blob update --content-type "image/jpeg" -c cdn -n

Begin by listing all blobs matching prefix in container container-name, selecting to output as tab separated values using az storage blob list -c <container-name> --prefix <prefix>. We pipe this to awk in order to select only the third (name) column and use grep to select only lines ending in .jpg. Finally we use xargs -n1 to pass each of the matching lines to az in order to set the content-type property to image/jpg for each of the blobs.