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You are here: manpages

curl

Section: curl Manual (1)
Updated: 202-0-19
Index Return to Main Contents

NAME

curl - transfer a URL

SYNOPSIS

curl [options / URLs]

DESCRIPTION

curl is a tool for transferring data from or to a server using URLs. It supports these protocols: DICT, FILE, FTP, FTPS, GOPHER, GOPHERS, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, MQTT, MQTTS, POP3, POP3S, RTMP, RTMPS, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET, TFTP, WS and WSS.

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

URL

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

If you provide a URL without a leading protocol:// scheme, curl guesses what protocol you want. It then defaults to HTTP but assumes others based on often-used hostname prefixes. For example, for hostnames starting with "ftp." curl assumes you want FTP.

You can specify any amount of URLs on the command line. They are fetched in a sequential manner in the specified order unless you use --parallel. You can specify command line options and URLs mixed and in any order on the command line.

curl attempts to reuse connections when doing multiple transfers, so that getting many files from the same server do not use multiple connects and setup handshakes. This improves speed. Connection reuse can only be done for URLs specified for a single command line invocation and cannot be performed between separate curl runs.

Provide an IPv6 zone id in the URL with an escaped percentage sign. Like in

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

Everything provided on the command line that is not a command line option or its argument, curl assumes is a URL and treats it as such.

GLOBBING

You can specify multiple URLs or parts of URLs by writing lists within braces or ranges within brackets. We call this "globbing".

Provide a list with three different names like this:

https://fun.example/{one,two,three}.jpg

sftp://{one,two,three}.example/README

Do sequences of alphanumeric series by using [] as in:

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

With leading zeroes:

ftp://ftp.example.com/file[001-100].txt

With letters through the alphabet:

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

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

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

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

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

https://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 aq&aq, aq?aq and aq*aq.

Switch off globbing with --globoff.

VARIABLES

curl supports command line variables (added in 8.3.0). Set variables with --variable name=content or --variable name@file (where "file" can be stdin if set to a single dash (-)).

Variable contents can be expanded in option parameters using "{{name}}" if the option name is prefixed with "--expand-". This gets the contents of the variable "name" inserted, or a blank if the name does not exist as a variable. Insert "{{" verbatim in the string by prefixing it with a backslash, like "{{".

You can access and expand environment variables by importing them with "--variable %name". This imports the variable called "name" but exits with an error if that environment variable is not already set. To provide a default value in case it is not already set, use "--variable %name=content" or "--variable %name@content".

Example: get the USER environment variable and expand into the URL, fail if USER is not set:

--variable aq%USERaq--expand-url = "https://example.com/api/{{USER}}/method"

When expanding variables, curl supports a set of functions that can make the variable contents more convenient to use. It can trim leading and trailing white space with "trim", output the contents as a JSON quoted string with "json", URL encode the string with "url", base64 encode it with "b64" and base64 decode it with "64dec". To apply functions to a variable expansion, add them colon separated to the right side of the variable. Variable content holding null bytes that are not encoded when expanded causes an error.

Example: get the contents of a file called $HOME/.secret into a variable called "fix". Make sure that the content is trimmed and percent-encoded when sent as POST data:

--variable %HOME--expand-variable fix@{{HOME}}/.secret--expand-data "{{fix:trim:url}}"
https://example.com/

Command line variables and expansions were added in 8.3.0.

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 works. Only absolute paths.
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 subscribing to a topic while uploading/posting equals publishing on a topic. MQTT over TLS is not supported (yet).
POP3(S): Downloading from a pop3 server means getting an email. With or without using TLS.
RTMP(S): The Realtime Messaging Protocol is primarily used to serve 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: Fetching 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.
WS(S): WebSocket done over HTTP/1. WSS implies that it works over HTTPS.

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 the transfer rate in bytes per second. The used suffixes ("k" for kilo, "M" for mega, "G" for giga, "T" for tera, "P" for peta and "E" for exa) are 1024 based. For example 1k is 1024 bytes. 1M is 1048576 bytes. Strictly speaking this makes the units kibibyte and mebibyte etc.

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.

VERSION

This man page describes curl 8.19.0. If you use a later version, chances are this man page does not fully document it. If you use an earlier version, this document tries to include version information about which specific version that introduced changes.

You can always learn which the latest curl version is by running

curl https://curl.se/info

The online version of this man page is always showing the latest incarnation: https://curl.se/docs/manpage.html

OPTIONS

Options start with one or two dashes. Many of the options require an additional value next to them. If provided text does not start with a dash, it is presumed to be and treated as a URL.

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-". In this list we mostly show the --option version of them.

When --next is used, it resets the parser state and you start again with a clean option state, except for the options that are global. Global options retain their values and meaning even after --next.

If the long option name ends with an equals sign ("="), the argument is the text following on its right side. (Added in 8.16.0)

The first argument that is exactly two dashes ("--"), marks the end of options; any argument after the end of options is interpreted as a URL argument even if it starts with a dash.

curl does little to no verification of the contents of command line arguments. Passing in "creative octets" like newlines might trigger unexpected results.

The following options are global: --fail-early, --libcurl, --parallel-immediate, --parallel-max-host, --parallel-max, --parallel, --progress-bar, --rate, --show-error, --stderr, --styled-output, --trace-ascii, --trace-config, --trace-ids, --trace-time, --trace and --verbose.

ALL OPTIONS

--abstract-unix-socket <path>

(HTTP) Connect to the server 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.

If --abstract-unix-socket is provided several times, the last set value is used.

Example:

curl-abstrac-uni-socket socketpath https://example.com

See also --proxy.

-I, --head

(HTTP FTP FILE) Fetch the headers only. HTTP-servers feature the command HEAD which this uses to get nothing but the header of a document. When used on an FTP or FILE URL, curl displays the file size and last modification time only.

Providing --head multiple times has no extra effect. Disable it again with --n-head.

Example:

curl-I https://example.com

See also --get, --verbose and --trace-ascii.

-H, --header <header/@file>

(HTTP IMAP SMTP) Extra header to include in information sent. When used within an HTTP request, it is added to the regular request headers.

For an IMAP or SMTP MIME uploaded mail built with --form options, it is prepended to the resulting MIME document, effectively including it at the mail global level. It does not affect raw uploaded mails.

You may specify any number of extra headers. Note that if you should add a custom header that has the same name as one of the internal ones curl would use, your externally set header is used instead of the internal one. This allows you to make even trickier stuff than curl would normally do. You should not replace internally set headers without knowing perfectly well what you are doing. Remove an internal header by giving a replacement without content on the right side of the colon, as in: -H "Host:". If you send the custom header with no-value then its header must be terminated with a semicolon, such as -H "X-Custom-Header;" to send "X-Custom-Header:".

curl makes sure that each header you add/replace is sent with the proper end-of-line marker, you should thus not add that as a part of the header content: do not add newlines or carriage returns, they only mess things up for you. curl passes on the verbatim string you give it without any filter or other safe guards. That includes white space and control characters.

This option can take an argument in @filename style, which then adds a header for each line in the input file. Using @- makes curl read the header file from stdin.

Please note that most anti-spam utilities check the presence and value of several MIME mail headers: these are "From:", "To:", "Date:" and "Subject:" among others and should be added with this option.

You need --proxy-header to send custom headers intended for an HTTP proxy.

Passing on a "Transfer-Encoding: chunked" header when doing an HTTP request with a request body, makes curl send the data using chunked encoding.

WARNING: headers set with this option are set in all HTTP requests - even after redirects are followed, like when told with --location. This can lead to the header being sent to other hosts than the original host, so sensitive headers should be used with caution combined with following redirects.

"Authorization:" and "Cookie:" headers are explicitly not passed on in HTTP requests when following redirects to other origins, unless --location-trusted is used.

--header can be used several times in a command line

Examples:

curl-H "-Firs-Name: Joe" https://example.com
curl-H "Use-Agent: ye-please/2000" https://example.com
curl-H "Host:" https://example.com
curl-H @headers.txt https://example.com

See also --user-agent, --referer and --proxy-header.

-h, --help <subject>

Usage help. Provide help for the subject given as an optional argument.

If no argument is provided, curl displays the most important command line arguments.

The argument can either be a category or a command line option. When a category is provided, curl shows all command line options within the given category. Specify category "all" to list all available options.

If "category" is specified, curl displays all available help categories.

If the provided subject is instead an existing command line option, specified either in its short form with a single dash and a single letter, or in the long form with two dashes and a longer name, curl displays a help text for that option in the terminal.

The help output is extensive for some options.

If the provided command line option is not known, curl says so.

Examples:

curl-help all
curl-help-insecure
curl-help-f

See also --proxy.

--ntlm

(HTTP) Use NTLM authentication. The NTLM authentication method was designed by Microsoft and is used by IIS web servers. It is a proprietary protocol, reverse-engineered by clever people and implemented in curl based on their efforts. This kind of behavior should not be endorsed, you should encourage everyone who uses NTLM to switch to a public and documented authentication method instead, such as Digest.

If you want to enable NTLM for your proxy authentication, then use --proxy-ntlm.

Providing --ntlm multiple times has no extra effect. Disable it again with --n-ntlm.

Example:

curl-ntlm-u user:password https://example.com

For --ntlm to work, it requires that the underlying libcurl is built to support TLS. See also --proxy-ntlm.

--ntlm-wb

(HTTP) Deprecated option (added in 8.8.0).

Enabled NTLM much in the style --ntlm does, but handed over the authentication to a separate executable that was executed when needed.

Providing --ntlm-wb multiple times has no extra effect.

Example:

curl-ntl-wb-u user:password https://example.com

See also --proxy.

-U, --proxy-user <user:password>

Specify the username and password to use for proxy authentication.

If you use a Windows SSPI-enabled curl binary and do either Negotiate or NTLM authentication then you can tell curl to select the username and password from your environment by specifying a single colon with this option: "-U :".

On systems where it works, curl hides the given option argument from process listings. This is not enough to protect credentials from possibly getting seen by other users on the same system as they still are visible for a moment before being cleared. Such sensitive data should be retrieved from a file instead or similar and never used in clear text in a command line.

If --proxy-user is provided several times, the last set value is used.

Example:

curl-prox-user smith:secret-x proxy https://example.com

See also --proxy.

--pubkey <key>

(SFTP SCP) Public key filename. Allows you to provide your public key in this separate file.

curl attempts to automatically extract the public key from the private key file, so passing this option is generally not required. Note that this public key extraction requires libcurl to be linked against a copy of libssh2 1.2.8 or higher that is itself linked against OpenSSL.

If --pubkey is provided several times, the last set value is used.

Example:

curl-pubkey file.pub sftp://example.com/

See also --socks5.

--socks5-gssapi

(GSS/kerberos) Use GSS-API authentication when connecting to a SOCKS5 proxy. The GSS-API authentication is enabled by default (if curl is compiled with GSS-API support). Use --socks5-basic to force username/password authentication to SOCKS5 proxies.

Providing --socks5-gssapi multiple times has no extra effect. Disable it again with --n-socks-gssapi.

Example:

curl-socks-gssapi-socks5 hostname:4096 https://example.com

See also --socks5.

--socks5-gssapi-nec

(GSS/kerberos) As part of the GSS-API negotiation a protection mode is negotiated. RFC 1961 says in section 4.3/4.4 it should be protected, but the NEC reference implementation does not. The option --socks5-gssapi-nec allows the unprotected exchange of the protection mode negotiation.

Providing --socks5-gssapi-nec multiple times has no extra effect. Disable it again with --n-socks-gssap-nec.

Example:

curl-socks-gssap-nec-socks5 hostname:4096 https://example.com

See also --socks5.

--socks5-gssapi-service <name>

Set the service name for a socks server. Default is rcmd/server-fqdn.

If --socks5-gssapi-service is provided several times, the last set value is used.

Example:

curl-socks-gssap-service sockd-socks5 hostname:4096 https://example.com

See also --socks5.

--socks5-hostname <host[:port]>

Use the specified SOCKS5 proxy (and let the proxy resolve the hostname). If the port number is not specified, it is assumed at port 1080.

To specify the proxy on a Unix domain socket, use localhost for host and append the absolute path to the domain socket. For example: "socks5h://localhost/path/to/socket.sock" (the scheme may be omitted).

This option overrides any previous use of --proxy, as they are mutually exclusive.

This option is superfluous since you can specify a socks5 hostname proxy with --proxy using a socks5h:// protocol prefix.

If --socks5-hostname is provided several times, the last set value is used.

Example:

curl-socks-hostname proxy.example:7000 https://example.com

This option is mutually exclusive with --proxy, --socks4, --socks4a and --socks5. See also --socks5 and --socks4a.

-Y, --speed-limit <speed>

If a transfer is slower than this set speed (in bytes per second) for a given number of seconds, it gets aborted. The time period is set with --speed-time and is 30 seconds by default.

If --speed-limit is provided several times, the last set value is used.

Example:

curl-spee-limit 300-spee-time 10 https://example.com

See also --speed-time, --limit-rate and --max-time.

-y, --speed-time <seconds>

If a transfer runs slower than speed-limit bytes per second during a speed-time period, the transfer is aborted. If speed-time is used, the default speed-limit is 1 unless set with --speed-limit.

This option controls transfers (in both directions) but does not affect slow connects etc. If this is a concern for you, try the --connect-timeout option.

If --speed-time is provided several times, the last set value is used.

Example:

curl-spee-limit 300-spee-time 10 https://example.com

See also --speed-limit and --limit-rate.

--ssl

(FTP IMAP POP3 SMTP LDAP) Warning: this is considered an insecure option. Consider using --ssl-reqd instead to be sure curl upgrades to a secure connection.

Try to use SSL/TLS for the connection - often referred to as STARTTLS or STLS because of the involved commands. Reverts to a non-secure connection if the server does not support SSL/TLS. See also --ftp-ssl-control and --ssl-reqd for different levels of encryption required.

This option is handled in LDAP (added in 7.81.0). It is fully supported by the OpenLDAP backend and ignored by the generic ldap backend.

Please note that a server may close the connection if the negotiation fails.

This option was formerly known as --ftp-ssl. That option name can still be used but might be removed in a future version.

Providing --ssl multiple times has no extra effect. Disable it again with --n-ssl.

Example:

curl-ssl pop3://example.com/

See also --ssl-reqd, --insecure and --ciphers.

--ssl-allow-beast

(TLS) Do not work around a security flaw in the TLS1.0 protocol known as BEAST. If this option is not used, the TLS layer may use workarounds known to cause interoperability problems with some older server implementations.

This option only changes how curl does TLS 1.0 and has no effect on later TLS versions.

WARNING: this option loosens the TLS security, and by using this flag you ask for exactly that.

Providing --ssl-allow-beast multiple times has no extra effect. Disable it again with --n-ss-allo-beast.

Example:

curl-ss-allo-beast https://example.com

See also --proxy-ssl-allow-beast and --insecure.

--ssl-auto-client-cert

(TLS) (Schannel) Automatically locate and use a client certificate for authentication, when requested by the server. Since the server can request any certificate that supports client authentication in the OS certificate store it could be a privacy violation and unexpected.

Providing --ssl-auto-client-cert multiple times has no extra effect. Disable it again with --n-ss-aut-clien-cert.

Example:

curl-ss-aut-clien-cert https://example.com

Added in 7.77.0. See also --proxy-ssl-auto-client-cert.

--ssl-no-revoke

(TLS) (Schannel) Disable certificate revocation checks. WARNING: this option loosens the SSL security, and by using this flag you ask for exactly that.

Providing --ssl-no-revoke multiple times has no extra effect. Disable it again with --n-ss-n-revoke.

Example:

curl-ss-n-revoke 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.

[ur-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 <comm-separated list of hosts/domains>

list of hostnames that should not go through any proxy. If set to an asterisk aq*aq 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
https://direct.example.com

accesses the target URL directly, and

NO_PROXY=direct.example.com curl -x http://proxy.example.com
https://somewhere.example.com

accesses the target URL through the proxy.

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

IP addresses can be specified using CIDR notation: an appended slash and number specifies the number of "network bits" out of the address to use in the comparison (added in 7.86.0). For example "192.168.0.0/16" would match all addresses starting with "192.168".

APPDATA <directory>

On Windows, this variable is used when trying to find the home directory. If the primary home variables are all unset.

COLUMNS <terminal width>

If set, the specified number of characters is used as the terminal width when the alternative progress-bar is shown. If not set, curl tries to figure it out using other ways.

CURL_CA_BUNDLE <file>

If set, it is used as the --cacert value. This environment variable is ignored if Schannel is used as the TLS backend.

CURL_HOME <directory>

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 makes curl stay with the default.

SSL backend names (case-insensitive): gnutls, mbedtls, openssl, rustls, schannel, wolfssl

HOME <directory>

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.

NETRC <path>

If set, this is used to find the ".netrc" file. It overrides all other netrc file location mechanisms and should be set to the full file path. (Added in curl 8.16.0)

QLOGDIR <directory>

If curl was built with HTTP/3 support, setting this environment variable to a local directory makes 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 the ngtcp2 and quiche QUIC backends.

SHELL

Used on VMS when trying to detect if using a DCL or a Unix shell.

SSL_CERT_DIR <directory>

If set, it is used as the --capath value. This environment variable is ignored if Schannel is used as the TLS backend.

SSL_CERT_FILE <path>

If set, it is used as the --cacert value. This environment variable is ignored if Schannel is used as the TLS backend.

SSLKEYLOGFILE <path>

If you set this environment variable to a filename, curl stores 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 (TLS 1.2 max), BoringSSL, GnuTLS, wolfSSL and Rustls.

USERPROFILE <directory>

On Windows, this variable is used when trying to find the home directory. If the other, primary, variables are all unset. If set, curl uses the path "$USERPROFILEApplication Data".

XDG_CONFIG_HOME <directory>

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 is 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 file system or similar.
25: Failed starting the upload. For FTP, the server typically denied the STOR command.
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.
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.
63: Maximum file size exceeded.
64: Requested FTP SSL level failed.
65: Sending the data requires a rewind that failed.
66: Failed to initialize SSL Engine.
67: The username, 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).
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 is queued.
90: SSL public key does not match 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.
97: Proxy handshake error.
98: A client-side certificate is required to complete the TLS handshake.
99: Poll or select returned fatal error.
100: A value or data field grew larger than allowed.
XX: More error codes might appear here in future releases. The existing ones are meant to never change.