NAME

       libcurl-env - environment variables libcurl understands

DESCRIPTION

       libcurl  reads and understands a set of environment variables that if set will control and
       change behaviors. This is the full list of variables to set and description of  what  they
       do.  Also  note that curl, the command line tool, supports a set of additional environment
       variables independently of this.

       [scheme]_proxy
              When libcurl is given a URL to use in a transfer, it first  extracts  the  "scheme"
              part  from  the  URL  and  checks  if  there  is  a given proxy set for that in its
              corresponding environment variable. A URL like "http://example.com" will hence  use
              the  "http_proxy"  variable,  while  a  URL  like  "ftp://example.com" will use the
              "ftp_proxy" variable.

              These proxy variables are also checked for in their uppercase versions, except  the
              "http_proxy" one which is only used lowercase. Note also that some systems actually
              have a case insensitve  handling  of  environment  variables  and  then  of  course
              "HTTP_PROXY" will still work...

       ALL_PROXY
              This  is a setting to set proxy for all URLs, independently of what scheme is being
              used. Note that the scheme specific variables will override this one if set.

       CURL_SSL_BACKEND
              When libcurl is built to support multiple SSL backends, it will select  a  specific
              backend  at  first  use. If no selection is done by the program using libcurl, this
              variable's selection will be used. It should be set to the full SSL backend name to
              use (case insensitve).

       HOME   When  the netrc feature is used (CURLOPT_NETRC(3)), this variable is checked as the
              primary way to find the "current" home directory in which the .netrc file is likely
              to exist.

       LOGNAME
              User name to use when invoking the ntlm-wb tool, if NTLMUSER wasn't set.

       NO_PROXY
              This  has the same functionality as the CURLOPT_NOPROXY(3) option: it gives libcurl
              a comma-separated list of host name patterns for which libcurl  should  not  use  a
              proxy.

       NTLMUSER
              User name to use when invoking the ntlm-wb tool.

       SSLKEYLOGFILE
              When  set  and  libcurl runs with a SSL backend that supports this feature, libcurl
              will save SSL secrets into the given file name.  Using  those  SSL  secrets,  other
              tools  (such  as  Wireshark) can decrypt the SSL communication and analyze/view the
              traffic.

       SSL_DIR
              When libcurl runs with the NSS backends for TLS features, this variable is used  to
              find the directory for NSS PKI database instead of the built-in.

       USER   User  name  to  use when invoking the ntlm-wb tool, if NTLMUSER and LOGNAME weren't
              set.

Debug Variables

       There's a set of variables only recognized and used if libcurl was buillt "debug enabled",
       which should never be true for a library used in production.

       CURL_GETHOSTNAME
              Debug-only variable.

       CURL_FORCETIME
              Debug-only variable.

       CURL_ENTROPY
              Debug-only  variable.  Used  to  set a fixed faked value to use instead of a proper
              random number so that functions  in  libcurl  that  are  otherwise  getting  random
              outputs can be tested for what they generate.

       CURL_TRACE
              Debug-only variable. Used for debugging the lib/ldap implementation.

       CURL_NTLM_WB_FILE
              Debug-only variable. Used to set to a debug-version of the ntlm-wb executable.

       CURL_OPENLDAP_TRACE
              Debug-only variable. Used for debugging the lib/openldap.c implementation.