Jon’s recent Find the Time to First Byte Using Curl post reminded me about the additional timing details that cURL can provide.
cURL supports formatted output for the details of the request ( see the cURL manpage for details, under “-w, –write-out <format>” ). For our purposes we’ll focus just on the timing details that are provided.
Step one: create a new file, curl.txt, and paste in:
time_namelookup: %{time_namelookup}n
time_connect: %{time_connect}n
time_appconnect: %{time_appconnect}n
time_pretransfer: %{time_pretransfer}n
time_redirect: %{time_redirect}n
time_starttransfer: %{time_starttransfer}n
----------n
time_total: %{time_total}n
content_type: %{content_type}n
filename_effective: %{filename_effective}n
http_code: %{http_code}n
ftp_entry_path: %{ftp_entry_path}n
http_connect: %{http_connect}n
local_ip: %{local_ip}n
local_port: %{local_port}n
num_connects: %{num_connects}n
num_redirects: %{num_redirects}n
redirect_url: %{redirect_url}n
remote_ip: %{remote_ip}n
remote_port: %{remote_port}n
size_download: %{size_download}n
size_header: %{size_header}n
size_request: %{size_request}n
size_upload: %{size_upload}n
speed_download: %{speed_download}n
speed_upload: %{speed_upload}n
ssl_verify_result: %{ssl_verify_result}n
url_effective: %{url_effective}n
Step two, make a request:
curl -w "@curl.txt" -o /dev/null -s http://www.aikaiyuan.com/
What this does:
-w "@curl-format.txt"tells cURL to use our format file-o /dev/nullredirects the output of the request to /dev/null-stells cURL not to show a progress meterhttp://wordpress.com/is the URL we are requesting
And here is what you get back:
time_namelookup: 0.007
time_connect: 0.053
time_appconnect: 0.000
time_pretransfer: 0.053
time_redirect: 0.000
time_starttransfer: 0.630
----------
time_total: 1.227
content_type: text/html; charset=UTF-8
curl: unknown --write-out variable: 'filename_effective'
filename_effective:
http_code: 200
ftp_entry_path:
http_connect: 000
curl: unknown --write-out variable: 'local_ip'
local_ip:
curl: unknown --write-out variable: 'local_port'
local_port:
num_connects: 1
num_redirects: 0
redirect_url:
curl: unknown --write-out variable: 'remote_ip'
remote_ip:
curl: unknown --write-out variable: 'remote_port'
remote_port:
size_download: 206721
size_header: 361
size_request: 170
size_upload: 0
speed_download: 168497.000
speed_upload: 0.000
ssl_verify_result: 0
url_effective: http://www.aikaiyuan.com/
Jon was looking specifically at time to first byte, which is the time_starttransfer line. The other timing details include DNS lookup, TCP connect, pre-transfer negotiations, redirects (in this case there were none), and of course the total time.
The format file for this output provides a reasonable level of flexibility, for instance you could make it CSV formatted for easy parsing. You might want to do that if you were running this as a cron job to track timing details of a specific URL.
For details on the other information that cURL can provide using -wcheck out the cURL manpage.
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