writeout.md

--write-out

--write-out or just -w for short, outputs text and information after a transfer is completed. It offers a large range of variables that you can include in the output, variables that have been set with values and information from the transfer.

Instruct curl to output a string by passing plain text to this option:

curl -w "formatted string" http://example.com/

…and you can also have curl read that string from a given file instead if you prefix the string with '@':

curl -w @filename http://example.com/

…or even have curl read the string from stdin if you use '-' as filename:

curl -w @- http://example.com/

Variables

The variables that are available are accessed by writing %{variable_name} in the string and that variable will then be substituted by the correct value. To output a plain % you write it as %%. You can also output a newline by using \n, a carriage return with \r and a tab space with \t.

As an example, we can output the Content-Type and the response code from an HTTP transfer, separated with newlines and some extra text like this:

curl -w "Type: %{content_type}\nCode: %{response_code}\n" http://example.com

The output is sent to stdout by default so you probably want to make sure that you do not also send the downloaded content to stdout as then you might have a hard time to separate out the data; or use %{stderr} to send the output to stderr.

HTTP headers

This option also provides an easy to use way to output the contents of HTTP response headers from the most recent transfer.

Use %header{name} in the string, where name is the case insensitive name of the header (without the trailing colon). The output header contents are then shown exactly as was sent over the network, with leading and trailing whitespace trimmed. Like this:

curl -w "Server: %header{server}\n" http://example.com

Windows

NOTE: In Windows, the %-symbol is a special symbol used to expand environment variables. In batch files all occurrences of % must be doubled when using this option to properly escape. If this option is used at the command prompt then the % cannot be escaped and unintended expansion is possible.

Available --write-out variables

Some of these variables are not available in really old curl versions.

Variable	Description
certs	Outputs the certificate chain from the most recent TLS handshake - with details. (Introduced in 7.88.0)
content_type	Content-Type of the requested document, if there was any.
errormsg	Error message from the transfer. Empty if no error occurred. (Introduced in 7.75.0)
exitcode	Numerical exit code from the transfer. 0 if no error occurred. (Introduced in 7.75.0)
filename_effective	The ultimate filename that curl writes out to. Practical if curl is told to write to a file with the --remote-name or --output option. It's most useful in combination with the --remote-header-name option.
ftp_entry_path	The initial path curl ended up in when logging on to the remote FTP server.
http_code	The former variable name for what is now known as response_code.
http_connect	the numerical code that was found in the last response (from a proxy) to a curl CONNECT request.
http_version	The HTTP version that was used.
json	all write-out variables as a single JSON object.
local_ip	IP address of the local end of the most recently used connection - can be either IPv4 or IPv6
local_port	Local port number of the most recently used connection
method	HTTP method the most recent request used
num_certs	Number of the certificates in the most recent TLS handshake. (Introduced in 7.88.0)
num_connects	Number of new connects made in the recent transfer.
num_headers	Number of response headers in the last response
num_redirects	Number of redirects that were followed in the request.
onerror	If the transfer ended with an error, show the rest of the string, otherwise stop here. (Introduced in 7.75.0)
proxy_ssl_verify_result	The result of the SSL peer certificate verification that was requested when communicating with a proxy. 0 means the verification was successful.
redirect_url	The actual URL a redirect would take you to when an HTTP request was made without -L to follow redirects.
remote_ip	The remote IP address of the most recently used connection — can be either IPv4 or IPv6.
remote_port	The remote port number of the most recently made connection.
response_code	The numerical response code that was found in the last transfer.
scheme	scheme used in the previous URL
size_download	Total number of bytes that were downloaded.
size_header	Total number of bytes of the downloaded headers.
size_request	Total number of bytes that were sent in the HTTP request.
size_upload	Total number of bytes that were uploaded.
speed_download	Average download speed that curl measured for the complete download in bytes per second.
speed_upload	Average upload speed that curl measured for the complete upload in bytes per second.
ssl_verify_result	the result of the SSL peer certificate verification that was requested. 0 means the verification was successful.
stderr	Makes the rest of the output get written to stderr.
stdout	makes the rest of the output get written to stdout.
time_appconnect	The time in seconds, it took from the start until the SSL/SSH/etc connect/handshake to the remote host was completed.
time_connect	The time in seconds, it took from the start until the TCP connect to the remote host (or proxy) was completed.
time_namelookup	The time in seconds, it took from the start until the name resolving was completed.
time_pretransfer	The time in seconds, it took from the start until the file transfer was just about to begin. This includes all pre-transfer commands and negotiations that are specific to the particular protocol(s) involved.
time_redirect	The time in seconds, it took for all redirection steps including name lookup, connect, pre-transfer and transfer before the final transaction was started. time_redirect the complete execution time for multiple redirections.
time_starttransfer	The time in seconds, it took from the start until the first byte was just about to be transferred. This includes time_pretransfer and also the time the server needed to calculate the result.
time_total	The total time in seconds, that the full operation lasted. The time will be displayed with millisecond resolution.
url	The URL used in the transfer. (Introduced in 7.75.0)
url_effective	The URL that was fetched last. This is particularly meaningful if you have told curl to follow Location: headers (with -L).
urlnum	0-based numerical index of the URL used in the transfer. (Introduced in 7.75.0)

In curl 8.1.0, variables to output only specific URL components were added. When the url or url_effective show more than you want.

Variable	Description
url.scheme	The scheme part of the URL that was fetched.
url.user	The user part of the URL that was fetched.
url.password	The password part of the URL that was fetched.
url.options	The options part of the URL that was fetched. Only available for some schemes.
url.host	The host name part of the URL that was fetched.
url.path	The path part of the URL that was fetched.
url.query	The query part of the URL that was fetched.
url.fragment	The fragment part of the URL that was fetched.
url.zoneid	The zone id part of the URL that was fetched. Only available if the host name is an IPv6 address.
urle.scheme	The scheme part of the effective (last) URL that was fetched.
urle.user	The user part of the effective (last) URL that was fetched.
urle.password	The password part of the effective (last) URL that was fetched.
urle.options	The options part of the effective (last) URL that was fetched. Only available for some schemes.
urle.host	The host name part of the effective (last) URL that was fetched.
urle.path	The path part of the effective (last) URL that was fetched.
urle.query	The query part of the effective (last) URL that was fetched.
urle.fragment	The fragment part of the effective (last) URL that was fetched.
urle.zoneid	The zone id part of the effective (last) URL that was fetched. Only available if the host name is an IPv6 address.