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author_name: Nick Frichette | ||
title: AWS CLI Tips and Tricks | ||
description: A collection of tips and tricks for using the AWS CLI. | ||
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# AWS CLI Tips and Tricks | ||
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## Standard Input/Output Redirection with "-" | ||
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!!! Warning | ||
The following examples have been tested in [bash](https://www.gnu.org/software/bash/) and [zsh](https://zsh.sourceforge.io/). Functionality may vary in other shells. If you find these commands work in additional environments, please open a pull request to update this note. | ||
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When working in an AWS environment, you may frequently need to view the contents of objects stored in S3. The traditional approach involves a two-step process: using [s3:cp](https://awscli.amazonaws.com/v2/documentation/api/latest/reference/s3/cp.html) to download the file to your local machine, then using `cat` or a similar tool to view it. While effective, this method can clutter your local system with temporary files and may be slower than necessary. | ||
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Fortunately, the AWS CLI allows us to simplify this process by using the `-` [character](https://www.baeldung.com/linux/dash-in-command-line-parameters) which represents standard input/output (STDIN/STDOUT). Using `-`, you can read or write file content directly from or to S3 without creating local copies. | ||
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### Reading from S3 | ||
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To read the contents of an object stored in S3 without having to download it first, use the following command: | ||
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```bash | ||
aws s3 cp s3://bucket-name/object-key - | ||
``` | ||
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Example: | ||
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```bash | ||
nick@host:~$ aws s3 cp s3://hackingthecloud/content - | ||
hacking the cloud | ||
``` | ||
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### Writing to S3 | ||
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To upload content directly to an object in S3 without a temporary file, use this command: | ||
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```bash | ||
echo "hacking the cloud" | aws s3 cp - s3://bucket-name/object-key | ||
``` | ||
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This command writes the specified text to an S3 object, again bypassing the need for a local file. | ||
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## Modifying the CloudTrail Log User-Agent with `AWS_EXECUTION_ENV` | ||
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!!! example "Shout-out" | ||
Shout-out to [Christophe Tafani-Dereeper](https://christophetd.fr/) for showing me this. | ||
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When making API calls to AWS, a `User-Agent` header is included in each request, containing details about the client making the request. Although it’s not possible to fully [customize](https://github.com/aws/aws-cli/issues/3990) this header, you can append information to it, which can be useful for tracking API calls in CloudTrail logs. | ||
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One way to modify the `User-Agent` is by setting the `AWS_EXECUTION_ENV` environment variable, used by AWS SDKs to identify the execution environment. Tools like [grimoire](https://github.com/DataDog/grimoire) leverage this variable to append custom information to the `User-Agent` header, making API tracking more informative. |