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.

libcurl 7.58.0                                  January 23, 2018                                  libcurl-env(3)