libcurl-env(3)

libcurl-env(3)    libcurl environment variables    libcurl-env(3)

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,  indepen-
          dently  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-

libcurl 7.58.0    Last change: January 23, 2018                 1

libcurl-env(3)    libcurl environment variables    libcurl-env(3)

          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  sup-
          ports  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 communi-
          cation 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  lib-
     curl  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    Last change: January 23, 2018                 2