JQ - Create .dockerconfigjson file

Use the jq tool to create a .dockerconfigjson file from existing details, including inline base64 encoding. Linux, bash style :

export REGISTRY="theregistry"
export EMAILADDRESS=eddie@example.com
export USER="eddie"
export PASSWORD="mysup3rp4ssw0rd"
jq --null-input --arg registry "$REGISTRY"                                                         \
                --arg emailaddress "$EMAILADDRESS"                                                 \
                --arg encodedcredentials $(echo "$USER:$PASSWORD" |  base64)                       \
                '{"auths": { ($registry): {"email": $emailaddress, "auth": $encodedcredentials}}}'

Powershell for those of us who are forced to (minus the email address):

$REGISTRY="theregistry"
$USER="eddie"
$PASSWORD="mysup3rp4ssw0rd"
jq --null-input --arg registry "$REGISTRY" `
                --arg encodedcredentials $([Convert]::ToBase64String([Text.Encoding]::UTF8.GetBytes("${USER}:${PASSWORD}"))) `
                '{"auths": { ($registry): {"auth": $encodedcredentials}}}' > .dockerconfigjson

Beware that the file produced in Powershell is subject to Windows’ bizarre encoding rules (UTF16, BOM etc). Here is a general use snippet that can sanitise the file for use elsewhere:

$MyRawString = Get-Content -Raw $pathtofile
$Utf8NoBomEncoding = New-Object System.Text.UTF8Encoding $False
[System.IO.File]::WriteAllLines($pathtofile, $MyRawString, $Utf8NoBomEncoding)