s3_file_exists
check if file exists in AWS S3
s3_dir_exists
check if path is a directory in AWS S3
Examples
if (FALSE) { # \dontrun{
# Require AWS S3 credentials
temp_file = s3_file_temp(tmp_dir= "MyBucket")
s3_file_create(temp_file)
s3_file_exists(temp_file)
} # }