libcurl-env.md (3123B)
1 --- 2 c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. 3 SPDX-License-Identifier: curl 4 Title: libcurl-env 5 Section: 3 6 Source: libcurl 7 See-also: 8 - libcurl-env-dbg (3) 9 Protocol: 10 - All 11 Added-in: n/a 12 --- 13 14 # NAME 15 16 libcurl-env - environment variables libcurl understands 17 18 # DESCRIPTION 19 20 libcurl reads and understands a set of environment variables that if set 21 controls and changes behaviors. This is the full list of variables to set and 22 description of what they do. Also note that curl, the command line tool, 23 supports a set of additional environment variables independently of this. 24 25 ## `[scheme]_proxy` 26 27 When libcurl is given a URL to use in a transfer, it first extracts the scheme 28 part from the URL and checks if there is a given proxy set for that in its 29 corresponding environment variable. A URL like https://example.com makes 30 libcurl use the **http_proxy** variable, while a URL like ftp://example.com 31 uses the **ftp_proxy** variable. 32 33 These proxy variables are also checked for in their uppercase versions, except 34 the **http_proxy** one which is only used lowercase. Note also that some 35 systems actually have a case insensitive handling of environment variables and 36 then of course **HTTP_PROXY** still works. 37 38 An exception exists for the WebSocket **ws** and **wss** URL schemes, where 39 libcurl first checks **ws_proxy** or **wss_proxy** but if they are not set, it 40 falls back and tries the http and https versions instead if set. 41 42 ## `ALL_PROXY` 43 44 This is a setting to set proxy for all URLs, independently of what scheme is 45 being used. Note that the scheme specific variables overrides this one if set. 46 47 ## `CURL_SSL_BACKEND` 48 49 When libcurl is built to support multiple SSL backends, it selects a specific 50 backend at first use. If no selection is done by the program using libcurl, 51 this variable's selection is used. Setting a name that is not a built-in 52 alternative makes libcurl stay with the default. 53 54 SSL backend names (case-insensitive): GnuTLS, mbedTLS, OpenSSL, Rustls, 55 Schannel, wolfSSL 56 57 ## `HOME` 58 59 When the netrc feature is used (CURLOPT_NETRC(3)), this variable is 60 checked as the primary way to find the "current" home directory in which 61 the .netrc file is likely to exist. 62 63 ## `USERPROFILE` 64 65 When the netrc feature is used (CURLOPT_NETRC(3)), this variable is 66 checked as the secondary way to find the "current" home directory (on Windows 67 only) in which the .netrc file is likely to exist. 68 69 ## `NO_PROXY` 70 71 This has the same functionality as the CURLOPT_NOPROXY(3) option: it 72 gives libcurl a comma-separated list of hostname patterns for which libcurl 73 should not use a proxy. 74 75 ## `SSLKEYLOGFILE` 76 77 When set and libcurl runs with an SSL backend that supports this feature, 78 libcurl saves SSL secrets into the given filename. Using those SSL secrets, 79 other tools (such as Wireshark) can decrypt the SSL communication and 80 analyze/view the traffic. 81 82 These secrets and this file might be sensitive. Users are advised to take 83 precautions so that they are not stolen or otherwise inadvertently revealed. 84 85 # Debug Variables 86 87 Debug variables are intended for internal use and are documented in 88 libcurl-env-dbg(3).