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curl(1)

curl Manual

curl(1)

NAME

curl - transfer a URL

SYNOPSIS

curl [options / URLs]

DESCRIPTION

curl is a tool for transferring data from or to a server. It supports these protocols: DICT, FILE, FTP, FTPS, GOPHER, GOPHERS, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, MQTT, POP3, POP3S, RTMP, RTMPS, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET or TFTP. The command is designed to work without user interaction.

curl offers a busload of useful tricks like proxy support, user authentication, FTP upload, HTTP post, SSL connections, cookies, file transfer resume and more. As you will see below, the number of features will make your head spin.

curl is powered by libcurl for all transfer-related features. See libcurl(3) for details.

URL

The URL syntax is protocol-dependent. You find a detailed description in RFC 3986.

You can specify multiple URLs or parts of URLs by writing part sets within braces and quoting the URL as in:

"http://site.{one,two,three}.com"

or you can get sequences of alphanumeric series by using [] as in:

"ftp://ftp.example.com/file[1-100].txt"

"ftp://ftp.example.com/file[001-100].txt" (with leading zeros)

"ftp://ftp.example.com/file[a-z].txt"

Nested sequences are not supported, but you can use several ones next to each other:

"http://example.com/archive[1996-1999]/vol[1-4]/part{a,b,c}.html"

You can specify any amount of URLs on the command line. They will be fetched in a sequential manner in the specified order. You can specify command line options and URLs mixed and in any order on the command line.

You can specify a step counter for the ranges to get every Nth number or letter:

"http://example.com/file[1-100:10].txt"

"http://example.com/file[a-z:2].txt"

When using [] or {} sequences when invoked from a command line prompt, you probably have to put the full URL within double quotes to avoid the shell from interfering with it. This also goes for other characters treated special, like for example '&', '?' and '*'.

Provide the IPv6 zone index in the URL with an escaped percentage sign and the interface name. Like in

"http://[fe80::3%25eth0]/"

If you specify URL without protocol:// prefix, curl will attempt to guess what protocol you might want. It will then default to HTTP but try other protocols based on often-used host name prefixes. For example, for host names starting with "ftp." curl will assume you want to speak FTP.

curl will do its best to use what you pass to it as a URL. It is not trying to validate it as a syntactically correct URL by any means but is fairly liberal with what it accepts.

curl will attempt to re-use connections for multiple file transfers, so that getting many files from the same server will not do multiple connects / handshakes. This improves speed. Of course this is only done on files specified on a single command line and cannot be used between separate curl invocations.

OUTPUT

If not told otherwise, curl writes the received data to stdout. It can be instructed to instead save that data into a local file, using the --output or --remote-name options. If curl is given multiple URLs to transfer on the command line, it similarly needs multiple options for where to save them.

curl does not parse or otherwise "understand" the content it gets or writes as output. It does no encoding or decoding, unless explicitly asked to with dedicated command line options.

PROTOCOLS

curl supports numerous protocols, or put in URL terms: schemes. Your particular build may not support them all.

DICT: Lets you lookup words using online dictionaries.

FILE: Read or write local files. curl does not support accessing file:// URL remotely, but when running on Microsoft Windows using the native UNC approach will work.

FTP(S): curl supports the File Transfer Protocol with a lot of tweaks and levers. With or without using TLS.

GOPHER(S): Retrieve files.

HTTP(S): curl supports HTTP with numerous options and variations. It can speak HTTP version 0.9, 1.0, 1.1, 2 and 3 depending on build options and the correct command line options.

IMAP(S): Using the mail reading protocol, curl can "download" emails for you. With or without using TLS.

LDAP(S): curl can do directory lookups for you, with or without TLS.

MQTT: curl supports MQTT version 3. Downloading over MQTT equals "subscribe" to a topic while uploading/posting equals "publish" on a topic. MQTT over TLS is not supported (yet).

POP3(S): Downloading from a pop3 server means getting a mail. With or without using TLS.

RTMP(S): The Realtime Messaging Protocol is primarily used to server streaming media and curl can download it.

RTSP: curl supports RTSP 1.0 downloads.

SCP: curl supports SSH version 2 scp transfers.

SFTP: curl supports SFTP (draft 5) done over SSH version 2.

SMB(S): curl supports SMB version 1 for upload and download.

SMTP(S): Uploading contents to an SMTP server means sending an email. With or without TLS.

TELNET: Telling curl to fetch a telnet URL starts an interactive session where it sends what it reads on stdin and outputs what the server sends it.

TFTP: curl can do TFTP downloads and uploads.

PROGRESS METER

curl normally displays a progress meter during operations, indicating the amount of transferred data, transfer speeds and estimated time left, etc. The progress meter displays number of bytes and the speeds are in bytes per second. The suffixes (k, M, G, T, P) are 1024 based. For example 1k is 1024 bytes. 1M is 1048576 bytes.

curl displays this data to the terminal by default, so if you invoke curl to do an operation and it is about to write data to the terminal, it disables the progress meter as otherwise it would mess up the output mixing progress meter and response data.

If you want a progress meter for HTTP POST or PUT requests, you need to redirect the response output to a file, using shell redirect (>), --output or similar.

This does not apply to FTP upload as that operation does not spit out any response data to the terminal.

If you prefer a progress "bar" instead of the regular meter, --progress-bar is your friend. You can also disable the progress meter completely with the --silent option.

OPTIONS

Options start with one or two dashes. Many of the options require an additional value next to them.

The short "single-dash" form of the options, -d for example, may be used with or without a space between it and its value, although a space is a recommended separator. The long "double-dash" form, --data for example, requires a space between it and its value.

Short version options that do not need any additional values can be used immediately next to each other, like for example you can specify all the options -O, -L and -v at once as -OLv.

In general, all boolean options are enabled with --option and yet again disabled with -- no-option. That is, you use the same option name but prefix it with "no-". However, in this list we mostly only list and show the --option version of them.

--abstract-unix-socket <path>: (HTTP) Connect through an abstract Unix domain socket, instead of using the network. Note: netstat shows the path of an abstract socket prefixed with '@', however the <path> argument should not have this leading character.

Example:
curl --abstract-unix-socket socketpath https://example.com

See also --unix-socket. Added in 7.53.0.

--alt-svc <file name>: (HTTPS) This option enables the alt-svc parser in curl. If the file name points to an existing alt-svc cache file, that will be used. After a completed transfer, the cache will be saved to the file name again if it has been modified.

Specify a "" file name (zero length) to avoid loading/saving and make curl just handle the cache in memory.

If this option is used several times, curl will load contents from all the files but the last one will be used for saving.

Example:
curl --alt-svc svc.txt https://example.com

See also --resolve and --connect-to. Added in 7.64.1.

--anyauth: (HTTP) Tells curl to figure out authentication method by itself, and use the most secure one the remote site claims to support. This is done by first doing a request and checking the response-headers, thus possibly inducing an extra network round-trip. This is used instead of setting a specific authentication method, which you can do with --basic, --digest, --ntlm, and --negotiate.

Using --anyauth is not recommended if you do uploads from stdin, since it may require data to be sent twice and then the client must be able to rewind. If the need should arise when uploading from stdin, the upload operation will fail.

Used together with -u, --user.

Example:
curl --anyauth --user me:pwd https://example.com

See also --proxy-anyauth, --basic and --digest.

-a, --append: (FTP SFTP) When used in an upload, this makes curl append to the target file instead of overwriting it. If the remote file does not exist, it will be created. Note that this flag is ignored by some SFTP servers (including OpenSSH).

Example:
curl --upload-file local --append ftp://example.com/

See also -r, --range and -C, --continue-at.

--aws-sigv4 <provider1[:provider2[:region[:service]]]>: Use AWS V4 signature authentication in the transfer.

The provider argument is a string that is used by the algorithm when creating outgoing authentication headers.

The region argument is a string that points to a geographic area of a resources collection (region-code) when the region name is omitted from the endpoint.

The service argument is a string that points to a function provided by a cloud (service-code) when the service name is omitted from the endpoint.

Example:
curl --aws-sigv4 "aws:amz:east-2:es" --user "key:secret" https://example.com

See also --basic and -u, --user. Added in 7.75.0.

--basic: (HTTP) Tells curl to use HTTP Basic authentication with the remote host. This is the default and this option is usually pointless, unless you use it to override a previously set option that sets a different authentication method (such as --ntlm, --digest, or --negotiate).

Used together with -u, --user.

Example:
curl -u name:password --basic https://example.com

See also --proxy-basic.

--cacert <file>: (TLS) Tells curl to use the specified certificate file to verify the peer. The file may contain multiple CA certificates. The certificate(s) must be in PEM format. Normally curl is built to use a default file for this, so this option is typically used to alter that default file.

curl recognizes the environment variable named 'CURL_CA_BUNDLE' if it is set, and uses the given path as a path to a CA cert bundle. This option overrides that variable.

The windows version of curl will automatically look for a CA certs file named 'curl-ca-bundle.crt', either in the same directory as curl.exe, or in the Current Working Directory, or in any folder along your PATH.

If curl is built against the NSS SSL library, the NSS PEM PKCS#11 module (libnsspem.so) needs to be available for this option to work properly.

(iOS and macOS only) If curl is built against Secure Transport, then this option is supported for backward compatibility with other SSL engines, but it should not be set. If the option is not set, then curl will use the certificates in the system and user Keychain to verify the peer, which is the preferred method of verifying the peer's certificate chain.

(Schannel only) This option is supported for Schannel in Windows 7 or later with libcurl 7.60 or later. This option is supported for backward compatibility with other SSL engines; instead it is recommended to use Windows' store of root certificates (the default for Schannel).

If this option is used several times, the last one will be used.

Example:
curl --cacert CA-file.txt https://example.com

See also --capath and -k, --insecure.

--capath <dir>: (TLS) Tells curl to use the specified certificate directory to verify the peer. Multiple paths can be provided by separating them with ":" (e.g. "path1:path2:path3"). The certificates must be in PEM format, and if curl is built against OpenSSL, the directory must have been processed using the c_rehash utility supplied with OpenSSL. Using --capath can allow OpenSSL-powered curl to make SSL-connections much more efficiently than using --cacert if the --cacert file contains many CA certificates.

If this option is set, the default capath value will be ignored, and if it is used several times, the last one will be used.

Example:
curl --capath /local/directory https://example.com

See also --cacert and -k, --insecure.

--cert-status: (TLS) Tells curl to verify the status of the server certificate by using the Certificate Status Request (aka. OCSP stapling) TLS extension.

If this option is enabled and the server sends an invalid (e.g. expired) response, if the response suggests that the server certificate has been revoked, or no response at all is received, the verification fails.

This is currently only implemented in the OpenSSL, GnuTLS and NSS backends.

Example:
curl --cert-status https://example.com

See also --pinnedpubkey. Added in 7.41.0.

--cert-type <type>: (TLS) Tells curl what type the provided client certificate is using. PEM, DER, ENG and P12 are recognized types.

The default type depends on the TLS backend and is usually PEM, however for Secure Transport and Schannel it is P12. If --cert is a pkcs11: URI then ENG is the default type.

If this option is used several times, the last one will be used.

Example:
curl --cert-type PEM --cert file https://example.com

See also -E, --cert, --key and --key-type.

-E, --cert <certificate[:password]>: (TLS) Tells curl to use the specified client certificate file when getting a file with HTTPS, FTPS or another SSL-based protocol. The certificate must be in PKCS#12 format if using Secure Transport, or PEM format if using any other engine. If the optional password is not specified, it will be queried for on the terminal. Note that this option assumes a "certificate" file that is the private key and the client certificate concatenated! See --cert and --key to specify them independently.

If curl is built against the NSS SSL library then this option can tell curl the nickname of the certificate to use within the NSS database defined by the environment variable SSL_DIR (or by default /etc/pki/nssdb). If the NSS PEM PKCS#11 module (libnsspem.so) is available then PEM files may be loaded. If you want to use a file from the current directory, please precede it with "./" prefix, in order to avoid confusion with a nickname. If the nickname contains ":", it needs to be preceded by "\" so that it is not recognized as password delimiter. If the nickname contains "\", it needs to be escaped as "\\" so that it is not recognized as an escape character.

If curl is built against OpenSSL library, and the engine pkcs11 is available, then a PKCS#11 URI (RFC 7512) can be used to specify a certificate located in a PKCS#11 device. A string beginning with "pkcs11:" will be interpreted as a PKCS#11 URI. If a PKCS#11 URI is provided, then the --engine option will be set as "pkcs11" if none was provided and the --cert-type option will be set as "ENG" if none was provided.

(iOS and macOS only) If curl is built against Secure Transport, then the certificate string can either be the name of a certificate/private key in the system or user keychain, or the path to a PKCS#12-encoded certificate and private key. If you want to use a file from the current directory, please precede it with "./" prefix, in order to avoid confusion with a nickname.

(Schannel only) Client certificates must be specified by a path expression to a certificate store. (Loading PFX is not supported; you can import it to a store first). You can use "<store location>\<store name>\<thumbprint>" to refer to a certificate in the system certificates store, for example, "CurrentUser\MY\934a7ac6f8a5d579285a74fa61e19f23ddfe8d7a". Thumbprint is usually a SHA-1 hex string which you can see in certificate details. Following store locations are supported: CurrentUser, LocalMachine, CurrentService, Services, CurrentUserGroupPolicy, LocalMachineGroupPolicy, LocalMachineEnterprise.

If this option is used several times, the last one will be used.

Example:
curl --cert certfile --key keyfile https://example.com

See also --cert-type, --key and --key-type.

--ciphers <list of ciphers>: (TLS) Specifies which ciphers to use in the connection. The list of ciphers must specify valid ciphers. Read up on SSL cipher list details on this URL:

https://curl.se/docs/ssl-ciphers.html

If this option is used several times, the last one will be used.

Example:
curl --ciphers ECDHE-ECDSA-AES256-CCM8 https://example.com

See also --tlsv1.3.

--compressed-ssh: (SCP SFTP) Enables built-in SSH compression. This is a request, not an order; the server may or may not do it.

Example:
curl --compressed-ssh sftp://example.com/

See also --compressed. Added in 7.56.0.

--compressed: (HTTP) Request a compressed response using one of the algorithms curl supports, and automatically decompress the content. Headers are not modified.

If this option is used and the server sends an unsupported encoding, curl will report an error. This is a request, not an order; the server may or may not deliver data compressed.

Example:
curl --compressed https://example.com

See also --compressed-ssh.

-K, --config <file>: Specify a text file to read curl arguments from. The command line arguments found in the text file will be used as if they were provided on the command line.

Options and their parameters must be specified on the same line in the file, separated by whitespace, colon, or the equals sign. Long option names can optionally be given in the config file without the initial double dashes and if so, the colon or equals characters can be used as separators. If the option is specified with one or two dashes, there can be no colon or equals character between the option and its parameter.

If the parameter contains whitespace (or starts with : or =), the parameter must be enclosed within quotes. Within double quotes, the following escape sequences are available: \\, \", \t, \n, \r and \v. A backslash preceding any other letter is ignored.

If the first column of a config line is a '#' character, the rest of the line will be treated as a comment.

Only write one option per physical line in the config file.

Specify the filename to --config as '-' to make curl read the file from stdin.

Note that to be able to specify a URL in the config file, you need to specify it using the --url option, and not by simply writing the URL on its own line. So, it could look similar to this:

url = "https://curl.se/docs/"

# --- Example file ---
# this is a comment
url = "example.com"
output = "curlhere.html"
user-agent = "superagent/1.0"

# and fetch another URL too
url = "example.com/docs/manpage.html"
-O
referer = "http://nowhereatall.example.com/"
# --- End of example file ---

When curl is invoked, it (unless --disable is used) checks for a default config file and uses it if found, even when --config is used. The default config file is checked for in the following places in this order:

1) "$CURL_HOME/.curlrc"

2) "$XDG_CONFIG_HOME/.curlrc" (Added in 7.73.0)

3) "$HOME/.curlrc"

4) Windows: "%USERPROFILE%\.curlrc"

5) Windows: "%APPDATA%\.curlrc"

6) Windows: "%USERPROFILE%\Application Data\.curlrc"

7) Non-Windows: use getpwuid to find the home directory

8) On Windows, if it finds no .curlrc file in the sequence described above, it checks for one in the same dir the curl executable is placed.

On Windows two filenames are checked per location: .curlrc and _curlrc, preferring the former. Older versions on Windows checked for _curlrc only.

This option can be used multiple times to load multiple config files.

Example:
curl --config file.txt https://example.com

See also -q, --disable.

--connect-timeout <fractional seconds>: Maximum time in seconds that you allow curl's connection to take. This only limits the connection phase, so if curl connects within the given period it will continue - if not it will exit. Since version 7.32.0, this option accepts decimal values.

If this option is used several times, the last one will be used.

Examples:
curl --connect-timeout 20 https://example.com
curl --connect-timeout 3.14 https://example.com

See also -m, --max-time.

--connect-to <HOST1:PORT1:HOST2:PORT2>: For a request to the given HOST1:PORT1 pair, connect to HOST2:PORT2 instead. This option is suitable to direct requests at a specific server, e.g. at a specific cluster node in a cluster of servers. This option is only used to establish the network connection. It does NOT affect the hostname/port that is used for TLS/SSL (e.g. SNI, certificate verification) or for the application protocols. "HOST1" and "PORT1" may be the empty string, meaning "any host/port". "HOST2" and "PORT2" may also be the empty string, meaning "use the request's original host/port".

A "host" specified to this option is compared as a string, so it needs to match the name used in request URL. It can be either numerical such as "127.0.0.1" or the full host name such as "example.org".

This option can be used many times to add many connect rules.

Example:
curl --connect-to example.com:443:example.net:8443 https://example.com

See also --resolve and -H, --header. Added in 7.49.0.

-C, --continue-at <offset>: Continue/Resume a previous file transfer at the given offset. The given offset is the exact number of bytes that will be skipped, counting from the beginning of the source file before it is transferred to the destination. If used with uploads, the FTP server command SIZE will not be used by curl.

Use "-C -" to tell curl to automatically find out where/how to resume the transfer. It then uses the given output/input files to figure that out.

If this option is used several times, the last one will be used.

Examples:
curl -C - https://example.com
curl -C 400 https://example.com

See also -r, --range.

-c, --cookie-jar <filename>: (HTTP) Specify to which file you want curl to write all cookies after a completed operation. Curl writes all cookies from its in-memory cookie storage to the given file at the end of operations. If no cookies are known, no data will be written. The file will be written using the Netscape cookie file format. If you set the file name to a single dash, "-", the cookies will be written to stdout.

This command line option will activate the cookie engine that makes curl record and use cookies. Another way to activate it is to use the --cookie option.

If the cookie jar cannot be created or written to, the whole curl operation will not fail or even report an error clearly. Using --verbose will get a warning displayed, but that is the only visible feedback you get about this possibly lethal situation.

If this option is used several times, the last specified file name will be used.

Examples:
curl -c store-here.txt https://example.com
curl -c store-here.txt -b read-these https://example.com

See also -b, --cookie.

-b, --cookie <data|filename>: (HTTP) Pass the data to the HTTP server in the Cookie header. It is supposedly the data previously received from the server in a "Set-Cookie:" line. The data should be in the format "NAME1=VALUE1; NAME2=VALUE2". This makes curl use the cookie header with this content explicitly in all outgoing request(s). If multiple requests are done due to authentication, followed redirects or similar, they will all get this cookie passed on.

If no '=' symbol is used in the argument, it is instead treated as a filename to read previously stored cookie from. This option also activates the cookie engine which will make curl record incoming cookies, which may be handy if you are using this in combination with the --location option or do multiple URL transfers on the same invoke. If the file name is exactly a minus ("-"), curl will instead read the contents from stdin.

The file format of the file to read cookies from should be plain HTTP headers (Set-Cookie style) or the Netscape/Mozilla cookie file format.

The file specified with --cookie is only used as input. No cookies will be written to the file. To store cookies, use the --cookie-jar option.

If you use the Set-Cookie file format and do not specify a domain then the cookie is not sent since the domain will never match. To address this, set a domain in Set-Cookie line (doing that will include sub-domains) or preferably: use the Netscape format.

This option can be used multiple times.

Users often want to both read cookies from a file and write updated cookies back to a file, so using both --cookie and --cookie-jar in the same command line is common.

Examples:
curl -b cookiefile https://example.com
curl -b cookiefile -c cookiefile https://example.com

See also -c, --cookie-jar and -j, --junk-session-cookies.

--create-dirs: When used in conjunction with the --output option, curl will create the necessary local directory hierarchy as needed. This option creates the directories mentioned with the --output option, nothing else. If the --output file name uses no directory, or if the directories it mentions already exist, no directories will be created.

Created dirs are made with mode 0750 on unix style file systems.

To create remote directories when using FTP or SFTP, try --ftp-create-dirs.

Example:
curl --create-dirs --output local/dir/file https://example.com

See also --ftp-create-dirs and --output-dir.

--create-file-mode <mode>: (SFTP SCP FILE) When curl is used to create files remotely using one of the supported protocols, this option allows the user to set which 'mode' to set on the file at creation time, instead of the default 0644.

This option takes an octal number as argument.

If this option is used several times, the last one will be used.

Example:
curl --create-file-mode 0777 -T localfile sftp://example.com/new

See also --ftp-create-dirs. Added in 7.75.0.

--crlf: (FTP SMTP) Convert LF to CRLF in upload. Useful for MVS (OS/390).

(SMTP added in 7.40.0)

Example:
curl --crlf -T file ftp://example.com/

See also -B, --use-ascii.

--crlfile <file>: (TLS) Provide a file using PEM format with a Certificate Revocation List that may specify peer certificates that are to be considered revoked.

If this option is used several times, the last one will be used.

Example:
curl --crlfile rejects.txt https://example.com

See also --cacert and --capath.

--curves <algorithm list>: (TLS) Tells curl to request specific curves to use during SSL session establishment according to RFC 8422, 5.1. Multiple algorithms can be provided by separating them with ":" (e.g. "X25519:P-521"). The parameter is available identically in the "openssl s_client/s_server" utilities.

--curves allows a OpenSSL powered curl to make SSL-connections with exactly the (EC) curve requested by the client, avoiding nontransparent client/server negotiations.

If this option is set, the default curves list built into openssl will be ignored.

Example:
curl --curves X25519 https://example.com

See also --ciphers. Added in 7.73.0.

--data-ascii <data>: (HTTP) This is just an alias for -d, --data.

Example:
curl --data-ascii @file https://example.com

See also --data-binary, --data-raw and --data-urlencode.

--data-binary <data>: (HTTP) This posts data exactly as specified with no extra processing whatsoever.

If you start the data with the letter @, the rest should be a filename. Data is posted in a similar manner as --data does, except that newlines and carriage returns are preserved and conversions are never done.

Like --data the default content-type sent to the server is application/x-www-form-urlencoded. If you want the data to be treated as arbitrary binary data by the server then set the content-type to octet-stream: -H "Content-Type: application/octet-stream".

If this option is used several times, the ones following the first will append data as described in -d, --data.

Example:
curl --data-binary @filename https://example.com

See also --data-ascii.

--data-raw <data>: (HTTP) This posts data similarly to --data but without the special interpretation of the @ character.

Examples:
curl --data-raw "hello" https://example.com
curl --data-raw "@at@at@" https://example.com

See also -d, --data. Added in 7.43.0.

--data-urlencode <data>: (HTTP) This posts data, similar to the other --data options with the exception that this performs URL-encoding.

To be CGI-compliant, the <data> part should begin with a name followed by a separator and a content specification. The <data> part can be passed to curl using one of the following syntaxes:

content: This will make curl URL-encode the content and pass that on. Just be careful so that the content does not contain any = or @ symbols, as that will then make the syntax match one of the other cases below!

=content: This will make curl URL-encode the content and pass that on. The preceding = symbol is not included in the data.

name=content: This will make curl URL-encode the content part and pass that on. Note that the name part is expected to be URL-encoded already.

@filename: This will make curl load data from the given file (including any newlines), URL-encode that data and pass it on in the POST.

name@filename: This will make curl load data from the given file (including any newlines), URL-encode that data and pass it on in the POST. The name part gets an equal sign appended, resulting in name=urlencoded-file-content. Note that the name is expected to be URL-encoded already.

Examples:
curl --data-urlencode name=val https://example.com
curl --data-urlencode =encodethis https://example.com
curl --data-urlencode name@file https://example.com
curl --data-urlencode @fileonly https://example.com

FILES

~/.curlrc

Default config file, see --config for details.

ENVIRONMENT

The environment variables can be specified in lower case or upper case. The lower case version has precedence. http_proxy is an exception as it is only available in lower case.

Using an environment variable to set the proxy has the same effect as using the --proxy option.

http_proxy [protocol://]<host>[:port]: Sets the proxy server to use for HTTP.

HTTPS_PROXY [protocol://]<host>[:port]: Sets the proxy server to use for HTTPS.

[url-protocol]_PROXY [protocol://]<host>[:port]: Sets the proxy server to use for [url-protocol], where the protocol is a protocol that curl supports and as specified in a URL. FTP, FTPS, POP3, IMAP, SMTP, LDAP, etc.

ALL_PROXY [protocol://]<host>[:port]: Sets the proxy server to use if no protocol-specific proxy is set.

NO_PROXY <comma-separated list of hosts/domains>: list of host names that should not go through any proxy. If set to an asterisk '*' only, it matches all hosts. Each name in this list is matched as either a domain name which contains the hostname, or the hostname itself.

This environment variable disables use of the proxy even when specified with the --proxy option. That is NO_PROXY=direct.example.com curl -x http://proxy.example.com http://direct.example.com accesses the target URL directly, and NO_PROXY=direct.example.com curl -x http://proxy.example.com http://somewhere.example.com accesses the target URL through the proxy.

The list of host names can also be include numerical IP addresses, and IPv6 versions should then be given without enclosing brackets.

IPv6 numerical addresses are compared as strings, so they will only match if the representations are the same: "::1" is the same as "::0:1" but they do not match.

APPDATA <dir>: On Windows, this variable is used when trying to find the home directory. If the primary home variable are all unset.

COLUMNS <terminal width>: If set, the specified number of characters will be used as the terminal width when the alternative progress-bar is shown. If not set, curl will try to figure it out using other ways.

CURL_CA_BUNDLE <file>: If set, will be used as the --cacert value.

CURL_HOME <dir>: If set, is the first variable curl checks when trying to find its home directory. If not set, it continues to check XDG_CONFIG_HOME.

CURL_SSL_BACKEND <TLS backend>: If curl was built with support for "MultiSSL", meaning that it has built-in support for more than one TLS backend, this environment variable can be set to the case insensitive name of the particular backend to use when curl is invoked. Setting a name that is not a built-in alternative will make curl stay with the default.

SSL backend names (case-insensitive): bearssl, gnutls, gskit, mbedtls, nss, openssl, rustls, schannel, secure-transport, wolfssl

HOME <dir>: If set, this is used to find the home directory when that is needed. Like when looking for the default .curlrc. CURL_HOME and XDG_CONFIG_HOME have preference.

QLOGDIR <directory name>: If curl was built with HTTP/3 support, setting this environment variable to a local directory will make curl produce qlogs in that directory, using file names named after the destination connection id (in hex). Do note that these files can become rather large. Works with both QUIC backends.

SHELL: Used on VMS when trying to detect if using a DCL or a "unix" shell.

SSL_CERT_DIR <dir>: If set, will be used as the --capath value.

SSL_CERT_FILE <path>: If set, will be used as the --cacert value.

SSLKEYLOGFILE <file name>: If you set this environment variable to a file name, curl will store TLS secrets from its connections in that file when invoked to enable you to analyze the TLS traffic in real time using network analyzing tools such as Wireshark. This works with the following TLS backends: OpenSSL, libressl, BoringSSL, GnuTLS, NSS and wolfSSL.

USERPROFILE <dir>: On Windows, this variable is used when trying to find the home directory. If the other, primary, variable are all unset. If set, curl will use the path "$USERPROFILE\Application Data".

XDG_CONFIG_HOME <dir>: If CURL_HOME is not set, this variable is checked when looking for a default .curlrc file.

PROXY PROTOCOL PREFIXES

The proxy string may be specified with a protocol:// prefix to specify alternative proxy protocols.

If no protocol is specified in the proxy string or if the string does not match a supported one, the proxy will be treated as an HTTP proxy.

The supported proxy protocol prefixes are as follows:

http://: Makes it use it as an HTTP proxy. The default if no scheme prefix is used.

https://: Makes it treated as an HTTPS proxy.

socks4://: Makes it the equivalent of --socks4

socks4a://: Makes it the equivalent of --socks4a

socks5://: Makes it the equivalent of --socks5

socks5h://: Makes it the equivalent of --socks5-hostname

EXIT CODES

There are a bunch of different error codes and their corresponding error messages that may appear under error conditions. At the time of this writing, the exit codes are:

0: Success. The operation completed successfully according to the instructions.

1: Unsupported protocol. This build of curl has no support for this protocol.

2: Failed to initialize.

3: URL malformed. The syntax was not correct.

4: A feature or option that was needed to perform the desired request was not enabled or was explicitly disabled at build-time. To make curl able to do this, you probably need another build of libcurl.

5: Could not resolve proxy. The given proxy host could not be resolved.

6: Could not resolve host. The given remote host could not be resolved.

7: Failed to connect to host.

8: Weird server reply. The server sent data curl could not parse.

9: FTP access denied. The server denied login or denied access to the particular resource or directory you wanted to reach. Most often you tried to change to a directory that does not exist on the server.

10: FTP accept failed. While waiting for the server to connect back when an active FTP session is used, an error code was sent over the control connection or similar.

11: FTP weird PASS reply. Curl could not parse the reply sent to the PASS request.

12: During an active FTP session while waiting for the server to connect back to curl, the timeout expired.

13: FTP weird PASV reply, Curl could not parse the reply sent to the PASV request.

14: FTP weird 227 format. Curl could not parse the 227-line the server sent.

15: FTP cannot use host. Could not resolve the host IP we got in the 227-line.

16: HTTP/2 error. A problem was detected in the HTTP2 framing layer. This is somewhat generic and can be one out of several problems, see the error message for details.

17: FTP could not set binary. Could not change transfer method to binary.

18: Partial file. Only a part of the file was transferred.

19: FTP could not download/access the given file, the RETR (or similar) command failed.

21: FTP quote error. A quote command returned error from the server.

22: HTTP page not retrieved. The requested URL was not found or returned another error with the HTTP error code being 400 or above. This return code only appears if --fail is used.

23: Write error. Curl could not write data to a local filesystem or similar.

25: FTP could not STOR file. The server denied the STOR operation, used for FTP uploading.

26: Read error. Various reading problems.

27: Out of memory. A memory allocation request failed.

28: Operation timeout. The specified time-out period was reached according to the conditions.

30: FTP PORT failed. The PORT command failed. Not all FTP servers support the PORT command, try doing a transfer using PASV instead!

31: FTP could not use REST. The REST command failed. This command is used for resumed FTP transfers.

33: HTTP range error. The range "command" did not work.

34: HTTP post error. Internal post-request generation error.

35: SSL connect error. The SSL handshaking failed.

36: Bad download resume. Could not continue an earlier aborted download.

37: FILE could not read file. Failed to open the file. Permissions?

38: LDAP cannot bind. LDAP bind operation failed.

39: LDAP search failed.

41: Function not found. A required LDAP function was not found.

42: Aborted by callback. An application told curl to abort the operation.

43: Internal error. A function was called with a bad parameter.

45: Interface error. A specified outgoing interface could not be used.

47: Too many redirects. When following redirects, curl hit the maximum amount.

48: Unknown option specified to libcurl. This indicates that you passed a weird option to curl that was passed on to libcurl and rejected. Read up in the manual!

49: Malformed telnet option.

51: The peer's SSL certificate or SSH MD5 fingerprint was not OK.

52: The server did not reply anything, which here is considered an error.

53: SSL crypto engine not found.

54: Cannot set SSL crypto engine as default.

55: Failed sending network data.

56: Failure in receiving network data.

58: Problem with the local certificate.

59: Could not use specified SSL cipher.

60: Peer certificate cannot be authenticated with known CA certificates.

61: Unrecognized transfer encoding.

62: Invalid LDAP URL.

63: Maximum file size exceeded.

64: Requested FTP SSL level failed.

65: Sending the data requires a rewind that failed.

66: Failed to initialise SSL Engine.

67: The user name, password, or similar was not accepted and curl failed to log in.

68: File not found on TFTP server.

69: Permission problem on TFTP server.

70: Out of disk space on TFTP server.

71: Illegal TFTP operation.

72: Unknown TFTP transfer ID.

73: File already exists (TFTP).

74: No such user (TFTP).

75: Character conversion failed.

76: Character conversion functions required.

77: Problem reading the SSL CA cert (path? access rights?).

78: The resource referenced in the URL does not exist.

79: An unspecified error occurred during the SSH session.

80: Failed to shut down the SSL connection.

82: Could not load CRL file, missing or wrong format.

83: Issuer check failed.

84: The FTP PRET command failed.

85: Mismatch of RTSP CSeq numbers.

86: Mismatch of RTSP Session Identifiers.

87: Unable to parse FTP file list.

88: FTP chunk callback reported error.

89: No connection available, the session will be queued.

90: SSL public key does not matched pinned public key.

91: Invalid SSL certificate status.

92: Stream error in HTTP/2 framing layer.

93: An API function was called from inside a callback.

94: An authentication function returned an error.

95: A problem was detected in the HTTP/3 layer. This is somewhat generic and can be one out of several problems, see the error message for details.

96: QUIC connection error. This error may be caused by an SSL library error. QUIC is the protocol used for HTTP/3 transfers.

XX: More error codes will appear here in future releases. The existing ones are meant to never change.

BUGS

If you experience any problems with curl, submit an issue in the project's bug tracker on GitHub: https://github.com/curl/curl/issues

AUTHORS / CONTRIBUTORS

Daniel Stenberg is the main author, but the whole list of contributors is found in the separate THANKS file.

WWW

https://curl.se