One can request only the headers using HTTP HEAD, as option -I
in curl(1)
.
$ curl -I /
Lengthy HTML response bodies are a pain to get in command-line, so I'd like to get only the header as feedback for my POST requests. However, HEAD and POST are two different methods.
How do I get cURL to display only response headers to a POST request?
-D, --dump-header <file>
Write the protocol headers to the specified file.
This option is handy to use when you want to store the headers
that a HTTP site sends to you. Cookies from the headers could
then be read in a second curl invocation by using the -b,
--cookie option! The -c, --cookie-jar option is however a better
way to store cookies.
and
-S, --show-error
When used with -s, --silent, it makes curl show an error message if it fails.
and
-L/--location
(HTTP/HTTPS) If the server reports that the requested page has moved to a different location (indicated with a Location: header and a 3XX response
code), this option will make curl redo the request on the new place. If used together with -i/--include or -I/--head, headers from all requested
pages will be shown. When authentication is used, curl only sends its credentials to the initial host. If a redirect takes curl to a different
host, it won’t be able to intercept the user+password. See also --location-trusted on how to change this. You can limit the amount of redirects to
follow by using the --max-redirs option.
When curl follows a redirect and the request is not a plain GET (for example POST or PUT), it will do the following request with a GET if the HTTP
response was 301, 302, or 303. If the response code was any other 3xx code, curl will re-send the following request using the same unmodified
method.
from the man page. so
curl -sSL -D - www.acooke.org -o /dev/null
follows redirects, dumps the headers to stdout and sends the data to /dev/null (that's a GET, not a POST, but you can do the same thing with a POST - just add whatever option you're already using for POSTing data)
note the -
after the -D
which indicates that the output "file" is stdout.
The other answers require the response body to be downloaded. But there's a way to make a POST request that will only fetch the header:
curl -s -I -X POST http://www.google.com
An -I
by itself performs a HEAD request which can be overridden by -X POST
to perform a POST (or any other) request and still only get the header data.
GET
request and doesn't download the whole response body (or at least doesn't output it). The -s
flag is nor necessary.
GET
with POST
in above command and it will work as expected. or any other
is key there.
POST
some data. Curl says: Warning: You can only select one HTTP request method! You asked for both POST Warning: (-d, --data) and HEAD (-I, --head).
-X HEAD
is no reliable solution here.
The Following command displays extra informations
curl -X POST http://httpbin.org/post -v > /dev/null
You can ask server to send just HEAD, instead of full response
curl -X HEAD -I http://httpbin.org/
Note:
In some cases, server may send different headers for POST and HEAD. But in almost all cases headers are same.
-X, --request
correctly, -X HEAD
still results in “a ton of data” but there is -I, --head
which should results in what you are anticipating.
-X HEAD
and -I
are exactly equivalent.
-X HEAD
is that the server might respond differently, since it now receives a HEAD
request instead of a GET
(or whatever the previous request was)
Warning: Setting custom HTTP method to HEAD with -X/--request may not work the Warning: way you want. Consider using -I/--head instead.
For long response bodies (and various other similar situations), the solution I use is always to pipe to less
, so
curl -i https://api.github.com/users | less
or
curl -s -D - https://api.github.com/users | less
will do the job.
HEAD
request to which many servers respond differently. the second issues a GET
request which is more like what we are looking for here.
Maybe it is little bit of an extreme, but I am using this super short version:
curl -svo. <URL>
Explanation:
-v
print debug information (which does include headers)
-o.
send web page data (which we want to ignore) to a certain file, .
in this case, which is a directory and is an invalid destination and makes the output to be ignored.
-s
no progress bar, no error information (otherwise you would see Warning: Failed to create the file .: Is a directory
)
warning: result always fails (in terms of error code, if reachable or not). Do not use in, say, conditional statements in shell scripting...
-o.
instead of -o /dev/null
?
-o.
is used versus -o /dev/null
for brevity
curl -svo. <url> && echo foo
won’t print foo
because -o.
make curl
return a non-zero (= error) code: curl: (23) Failed writing body
.
Much easier – this also follows links.
curl -IL http://example.com/in-the-shadows
While the other answers have not worked for me in all situations, the best solution I could find (working with POST
as well), taken from here:
curl -vs 'https://some-site.com' 1> /dev/null
headcurl.cmd (windows version)
curl -sSkv -o NUL %* 2>&1
I don't want a progress bar -s,
but I do want errors -S,
not bothering about valid https certificates -k,
getting high verbosity -v (this is about troubleshooting, is it?),
no output (in a clean way).
oh, and I want to forward stderr to stdout, so I can grep against the whole thing (since most or all output comes in stderr)
%* means [pass on all parameters to this script] (well(https://stackoverflow.com/a/980372/444255), well usually that's just one parameter: the url you are testing
real-world example (on troubleshooting proxy issues):
C:\depot>headcurl google.ch | grep -i -e http -e cache
Hostname was NOT found in DNS cache
GET HTTP://google.ch/ HTTP/1.1
HTTP/1.1 301 Moved Permanently
Location: http://www.google.ch/
Cache-Control: public, max-age=2592000
X-Cache: HIT from company.somewhere.ch
X-Cache-Lookup: HIT from company.somewhere.ch:1234
Linux version
for your .bash_aliases
/ .bash_rc
:
alias headcurl='curl -sSkv -o /dev/null $@ 2>&1'
-X POST
to the passthrough parameters, if you want GET, use GET (i.e. default), as responses may differ. - Unless you do heavy curling in production scripts (not for diagnosis anddevelopment) I don't care about a bit of bandwidth.
Success story sharing
curl -s -D - http://yahoo.com -o nul
-D
takes an argument that says where the output should go. the single dash means it should go to stdout.