Loading AWS CLI parameters from a file - AWS Command Line Interface

Loading AWS CLI parameters from a file

Some parameters expect file names as arguments, from which the AWS CLI loads the data. Other parameters enable you to specify the parameter value as either text typed on the command line or read from a file. Whether a file is required or optional, you must encode the file correctly so that the AWS CLI can understand it. The file's encoding must match the reading system's default locale. You can determine this by using the Python locale.getpreferredencoding() method.


By default, Windows PowerShell outputs text as UTF-16, which conflicts with the UTF-8 encoding used by many Linux systems. We recommend that you use -Encoding ascii with your PowerShell Out-File commands to ensure the AWS CLI can read the resulting file.

Sometimes it's convenient to load a parameter value from a file instead of trying to type it all as a command line parameter value, such as when the parameter is a complex JSON string. To specify a file that contains the value, specify a file URL in the following format.


The first two slash '/' characters are part of the specification. If the required path begins with a '/', the result is three slash characters: file:///folder/file.

The URL provides the path to the file that contains the actual parameter content.


This behavior is disabled automatically for parameters that already expect a URL, such as parameter that identifies a AWS CloudFormation template URL.

You can also disable this behavior by adding the following line to your CLI configuration file.

cli_follow_urlparam = false

The file paths in the following examples are interpreted to be relative to the current working directory.

Linux or macOS

// Read from a file in the current directory $ aws ec2 describe-instances --filters file://filter.json // Read from a file in /tmp $ aws ec2 describe-instances --filters file:///tmp/filter.json


// Read from a file in C:\temp C:\> aws ec2 describe-instances --filters file://C:\temp\filter.json

The file:// prefix option supports Unix-style expansions, including "~/", "./", and "../". On Windows, the "~/" expression expands to your user directory, stored in the %USERPROFILE% environment variable. For example, on Windows 10 you would typically have a user directory under C:\Users\User Name\.

You must still escape JSON documents that are embedded as the value of another JSON document.

$ aws sqs create-queue --queue-name my-queue --attributes file://attributes.json


{ "RedrivePolicy": "{\"deadLetterTargetArn\":\"arn:aws:sqs:us-west-2:0123456789012:deadletter\", \"maxReceiveCount\":\"5\"}" }

Binary files

For commands that take binary data as a parameter, specify that the data is binary content by using the fileb:// prefix. Commands that accept binary data include:

  • aws ec2 run-instances--user-data parameter.

  • aws s3api put-object--sse-customer-key parameter.

  • aws kms decrypt--ciphertext-blob parameter.

The following example generates a binary 256-bit AES key using a Linux command line tool, and then provides it to Amazon S3 to encrypt an uploaded file server-side.

$ dd if=/dev/urandom bs=1 count=32 > sse.key 32+0 records in 32+0 records out 32 bytes (32 B) copied, 0.000164441 s, 195 kB/s $ aws s3api put-object --bucket my-bucket --key test.txt --body test.txt --sse-customer-key fileb://sse.key --sse-customer-algorithm AES256 { "SSECustomerKeyMD5": "iVg8oWa8sy714+FjtesrJg==", "SSECustomerAlgorithm": "AES256", "ETag": "\"a6118e84b76cf98bf04bbe14b6045c6c\"" }

Remote files

The AWS CLI also supports loading parameters from a file hosted on the internet with an http:// or https:// URL. The following example references a file stored in an Amazon S3 bucket. This allows you to access parameter files from any computer, but it does require that the container is publicly accessible.

$ aws ec2 run-instances --image-id ami-12345678 --block-device-mappings http://my-bucket.s3.amazonaws.com/filename.json

The preceding example assumes that the file filename.json contains the following JSON data.

[ { "DeviceName": "/dev/sdb", "Ebs": { "VolumeSize": 20, "DeleteOnTermination": false, "VolumeType": "standard" } } ]

For another example referencing a file containing more complex JSON-formatted parameters, see Attaching an IAM managed policy to an IAM user.