125 lines
3.6 KiB
Markdown
125 lines
3.6 KiB
Markdown
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---
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c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
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SPDX-License-Identifier: curl
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Title: curl_global_trace
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Section: 3
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Source: libcurl
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See-also:
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- curl_global_init (3)
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- libcurl (3)
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---
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# NAME
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curl_global_trace - Global libcurl logging configuration
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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CURLcode curl_global_trace(const char *config);
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~~~
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# DESCRIPTION
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This function configures the logging behavior, allowing to make some
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parts of curl more verbose or silent than others.
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This function may be called during the initialization phase of a program. It
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does not have to be. It can be called several times even, possibly overwriting
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settings of previous calls.
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Calling this function after transfers have been started is undefined. On
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some platforms/architectures it might take effect, on others not.
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This function is thread-safe since libcurl 8.3.0 if
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curl_version_info(3) has the CURL_VERSION_THREADSAFE feature bit set
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(most platforms).
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If this is not thread-safe, you must not call this function when any other
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thread in the program (i.e. a thread sharing the same memory) is running.
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This does not just mean no other thread that is using libcurl. Because
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curl_global_init(3) may call functions of other libraries that are
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similarly thread unsafe, it could conflict with any other thread that uses
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these other libraries.
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If you are initializing libcurl from a Windows DLL you should not initialize
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it from *DllMain* or a static initializer because Windows holds the loader
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lock during that time and it could cause a deadlock.
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The *config* string is a list of comma-separated component names. Names
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are case-insensitive and unknown names are ignored. The special name "all"
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applies to all components. Names may be prefixed with '+' or '-' to enable
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or disable detailed logging for a component.
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The list of component names is not part of curl's public API. Names may be
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added or disappear in future versions of libcurl. Since unknown names are
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silently ignored, outdated log configurations does not cause errors when
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upgrading libcurl. Given that, some names can be expected to be fairly stable
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and are listed below for easy reference.
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Note that log configuration applies only to transfers where debug logging
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is enabled. See CURLOPT_VERBOSE(3) or CURLOPT_DEBUGFUNCTION(3)
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on how to control that.
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# TRACE COMPONENTS
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## tcp
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Tracing of TCP socket handling: connect, reads, writes.
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## ssl
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Tracing of SSL/TLS operations, whichever SSL backend is used in your build.
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## http/2
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Details about HTTP/2 handling: frames, events, I/O, etc.
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## http/3
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Details about HTTP/3 handling: connect, frames, events, I/O etc.
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## http-proxy
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Involved when transfers are tunneled through an HTTP proxy. "h1-proxy" or
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"h2-proxy" are also involved, depending on the HTTP version negotiated with
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the proxy.
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In order to find out all components involved in a transfer, run it with "all"
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configured. You can then see all names involved in your libcurl version in the
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trace.
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# EXAMPLE
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~~~c
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int main(void)
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{
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/* log details of HTTP/2 and SSL handling */
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curl_global_trace("http/2,ssl");
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/* log all details, except SSL handling */
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curl_global_trace("all,-ssl");
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}
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~~~
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Below is a trace sample where "http/2" was configured. The trace output
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of an enabled component appears at the beginning in brackets.
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~~~
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* [HTTP/2] [h2sid=1] cf_send(len=96) submit https://example.com/
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...
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* [HTTP/2] [h2sid=1] FRAME[HEADERS]
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* [HTTP/2] [h2sid=1] 249 header bytes
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...
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~~~
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# AVAILABILITY
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Added in 8.3
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# RETURN VALUE
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If this function returns non-zero, something went wrong and the configuration
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may not have any effects or may only been applied partially.
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