Are files from /tmp automatically deleted by AWS Lambda?

Question

Does AWS clear the /tmp directory automatically?

Is there a flush() sort of function? If not, how can I remove/delete all the files from the /tmp folder?

I have an AWS Lambda function where I download a file to my /tmp folder. I unzip the zipped file and gzip all individual files. All this happens within the /tmp directory and before I upload the gzipped files to S3 again.

Afterwards, I no longer need the files in my /tmp folder & would like to clear the directory.

If I open /tmp from my local macOS machine, I don't see any related files at all so I am not sure how to check if they are successfully deleted or not.

Ermiya Eskandary · Accepted Answer · 2021-10-25T13:58:12.560

4

No, files from /tmp are not automatically deleted.

The AWS Lambda FAQs state:

To improve performance, AWS Lambda may choose to retain an instance of your function and reuse it to serve a subsequent request, rather than creating a new copy. To learn more about how Lambda reuses function instances, visit our documentation. Your code should not assume that this will always happen.

As per the above doc and experience, you may find an empty or "pre-used" /tmp directory depending on if AWS Lambda has reused a previous Lambda environment for your current request.

This may, or may not be suitable depending on the use case & there's no guarantees so if you need to ensure a clean /tmp directory on every function invocation, clear the /tmp directory yourself.

Is there a flush() sort of function?

No, AWS does not (& shouldn't) offer a way programmatically via their SDK as this is related to file I/O.

How to delete all files inside the /tmp directory will be dependent on the Lambda function runtime.

For Python, try:

from subprocess import call
...
call('rm -rf /tmp/*', shell=True)

edited Oct 25 '21 at 13:58

answered Oct 25 '21 at 10:23

Ermiya Eskandary

15,323
3
31
44

how can I specify a file name here? a particular file to be deleted from tmp. Variable form – x89 Oct 26 '21 at 13:08
`call('rm -rf /tmp/' + 'myspecialfile.txt', shell=True)` - replace `myspecialfile.txt` with your variable – Ermiya Eskandary Oct 26 '21 at 13:09
I meant variable outside the call function...so I can run it in a loop – x89 Oct 26 '21 at 13:17
Specify the variable outside then use inside - it's just like any other Python code :) then call `call` as many times as you like – Ermiya Eskandary Oct 26 '21 at 13:18
I tried this ```filename = 'test' call(f"rm -rf /tmp/{filename}", shell=True)```but throws an invalid syntax error – x89 Oct 26 '21 at 13:19
Try `filename = 'test' call("rm -rf /tmp/" + filename, shell=True)` – Ermiya Eskandary Oct 26 '21 at 13:21

Are files from /tmp automatically deleted by AWS Lambda?

1 Answers1