1<!-- Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. --> 2<!-- SPDX-License-Identifier: curl --> 3# ENVIRONMENT 4The environment variables can be specified in lower case or upper case. The 5lower case version has precedence. `http_proxy` is an exception as it is only 6available in lower case. 7 8Using an environment variable to set the proxy has the same effect as using 9the --proxy option. 10 11## `http_proxy` [protocol://]<host>[:port] 12Sets the proxy server to use for HTTP. 13 14## `HTTPS_PROXY` [protocol://]<host>[:port] 15Sets the proxy server to use for HTTPS. 16 17## `[url-protocol]_PROXY` [protocol://]<host>[:port] 18Sets the proxy server to use for [url-protocol], where the protocol is a 19protocol that curl supports and as specified in a URL. FTP, FTPS, POP3, IMAP, 20SMTP, LDAP, etc. 21 22## `ALL_PROXY` [protocol://]<host>[:port] 23Sets the proxy server to use if no protocol-specific proxy is set. 24 25## `NO_PROXY` <comma-separated list of hosts/domains> 26list of hostnames that should not go through any proxy. If set to an asterisk 27'*' only, it matches all hosts. Each name in this list is matched as either a 28domain name which contains the hostname, or the hostname itself. 29 30This environment variable disables use of the proxy even when specified with 31the --proxy option. That is 32 33 NO_PROXY=direct.example.com curl -x http://proxy.example.com 34 http://direct.example.com 35 36accesses the target URL directly, and 37 38 NO_PROXY=direct.example.com curl -x http://proxy.example.com 39 http://somewhere.example.com 40 41accesses the target URL through the proxy. 42 43The list of hostnames can also be include numerical IP addresses, and IPv6 44versions should then be given without enclosing brackets. 45 46IP addresses can be specified using CIDR notation: an appended slash and 47number specifies the number of "network bits" out of the address to use in the 48comparison (added in 7.86.0). For example "192.168.0.0/16" would match all 49addresses starting with "192.168". 50 51## `APPDATA` <dir> 52On Windows, this variable is used when trying to find the home directory. If 53the primary home variable are all unset. 54 55## `COLUMNS` <terminal width> 56If set, the specified number of characters is used as the terminal width when 57the alternative progress-bar is shown. If not set, curl tries to figure it out 58using other ways. 59 60## `CURL_CA_BUNDLE` <file> 61If set, it is used as the --cacert value. This environment variable is ignored 62if Schannel is used as the TLS backend. 63 64## `CURL_HOME` <dir> 65If set, is the first variable curl checks when trying to find its home 66directory. If not set, it continues to check *XDG_CONFIG_HOME* 67 68## `CURL_SSL_BACKEND` <TLS backend> 69If curl was built with support for "MultiSSL", meaning that it has built-in 70support for more than one TLS backend, this environment variable can be set to 71the case insensitive name of the particular backend to use when curl is 72invoked. Setting a name that is not a built-in alternative makes curl stay 73with the default. 74 75SSL backend names (case-insensitive): **bearssl**, **gnutls**, **mbedtls**, 76**openssl**, **rustls**, **schannel**, **secure-transport**, **wolfssl** 77 78## `HOME` <dir> 79If set, this is used to find the home directory when that is needed. Like when 80looking for the default .curlrc. *CURL_HOME* and *XDG_CONFIG_HOME* 81have preference. 82 83## `QLOGDIR` <directory name> 84If curl was built with HTTP/3 support, setting this environment variable to a 85local directory makes curl produce **qlogs** in that directory, using file 86names named after the destination connection id (in hex). Do note that these 87files can become rather large. Works with the ngtcp2 and quiche QUIC backends. 88 89## `SHELL` 90Used on VMS when trying to detect if using a **DCL** or a **Unix** shell. 91 92## `SSL_CERT_DIR` <dir> 93If set, it is used as the --capath value. This environment variable is ignored 94if Schannel is used as the TLS backend. 95 96## `SSL_CERT_FILE` <path> 97If set, it is used as the --cacert value. This environment variable is ignored 98if Schannel is used as the TLS backend. 99 100## `SSLKEYLOGFILE` <filename> 101If you set this environment variable to a filename, curl stores TLS secrets 102from its connections in that file when invoked to enable you to analyze the 103TLS traffic in real time using network analyzing tools such as Wireshark. This 104works with the following TLS backends: OpenSSL, LibreSSL (TLS 1.2 max), 105BoringSSL, GnuTLS and wolfSSL. 106 107## `USERPROFILE` <dir> 108On Windows, this variable is used when trying to find the home directory. If 109the other, primary, variable are all unset. If set, curl uses the path 110**"$USERPROFILE\Application Data"**. 111 112## `XDG_CONFIG_HOME` <dir> 113If *CURL_HOME* is not set, this variable is checked when looking for a 114default .curlrc file. 115
