gnurl_easy_setopt(3)

🎀 gnurl_easy_setopt(3) — libgnurl Manual 🎀

okay bestie, buckle up — this is the function. everything you're about to read lives in the libgnurl Manual, and it's a long one, so hydrate first 💖

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✨ NAME ✨

curl_easy_setopt — the one that sets options for a curl easy handle 🫶

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✨ SYNOPSIS ✨

#include <gnurl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLoption option, parameter);

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💅 DESCRIPTION 💅

so curl_easy_setopt(3) is literally the way you tell libcurl how to behave. set the right options and your app gets to change libcurl's whole behavior, no cap. every option gets set with an option followed by a parameter — and that parameter can be a long, a function pointer, an object pointer, or a curl_off_t, depending on what that specific option expects. so like… read this manual carefully, fr fr, because bad input values may cause libcurl to behave badly 😭

you can only set one option in each function call. a typical application uses many curl_easy_setopt(3) calls in the setup phase. many. like, a lot. it's giving character development.

options you set with this function call are valid for all forthcoming transfers performed using this handle. and here's the thing — the options are not in any way reset between transfers, so if you want subsequent transfers with different options, you gotta change them between the transfers. you can optionally reset all options back to internal default with curl_easy_reset(3) though, iconic of it ✨

strings passed to libcurl as 'char *' arguments are copied by the library 🎀 so the string storage associated to the pointer argument may be overwritten after curl_easy_setopt(3) returns. the only exception to this rule is really CURLOPT_POSTFIELDS(3), but the alternative that copies the string, CURLOPT_COPYPOSTFIELDS(3), has some usage characteristics you need to read up on 👀 (iykyk).

the order in which the options are set does not matter. periodt. 💅

okay history lesson: before version 7.17.0, strings were not copied. instead the user was forced keep them available until libcurl no longer needed them. so yeah, if you're in your time-travel era, watch out 🕰️

and the handle — that's the return code from a curl_easy_init(3) or curl_easy_duphandle(3) call. that's your main character. 🎀

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🌸 BEHAVIOR OPTIONS 🌸

• CURLOPT_VERBOSE — display verbose information ✨ see CURLOPT_VERBOSE(3)
• CURLOPT_HEADER — include the header in the body output 💌 see CURLOPT_HEADER(3)
• CURLOPT_NOPROGRESS — shut off the progress meter 🙈 see CURLOPT_NOPROGRESS(3)
• CURLOPT_NOSIGNAL — do not install signal handlers 🚫 see CURLOPT_NOSIGNAL(3)
• CURLOPT_WILDCARDMATCH — transfer multiple files according to a file name pattern 🦋 see CURLOPT_WILDCARDMATCH(3)

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🌈 CALLBACK OPTIONS 🌈

like, this is the callback era and we're all just living in it 🫶

• CURLOPT_WRITEFUNCTION — callback for writing data ✍️ see CURLOPT_WRITEFUNCTION(3)
• CURLOPT_WRITEDATA — data pointer to pass to the write callback 🎀 see CURLOPT_WRITEDATA(3)
• CURLOPT_READFUNCTION — callback for reading data 📖 see CURLOPT_READFUNCTION(3)
• CURLOPT_READDATA — data pointer to pass to the read callback 🌸 see CURLOPT_READDATA(3)
• CURLOPT_IOCTLFUNCTION — callback for I/O operations ⚙️ see CURLOPT_IOCTLFUNCTION(3)
• CURLOPT_IOCTLDATA — data pointer to pass to the I/O callback 💜 see CURLOPT_IOCTLDATA(3)
• CURLOPT_SEEKFUNCTION — callback for seek operations 🔍 see CURLOPT_SEEKFUNCTION(3)
• CURLOPT_SEEKDATA — data pointer to pass to the seek callback 🦋 see CURLOPT_SEEKDATA(3)
• CURLOPT_SOCKOPTFUNCTION — callback for sockopt operations 🧦 see CURLOPT_SOCKOPTFUNCTION(3)
• CURLOPT_SOCKOPTDATA — data pointer to pass to the sockopt callback 🎀 see CURLOPT_SOCKOPTDATA(3)
• CURLOPT_OPENSOCKETFUNCTION — callback for socket creation 🔌 see CURLOPT_OPENSOCKETFUNCTION(3)
• CURLOPT_OPENSOCKETDATA — data pointer to pass to the open socket callback ✨ see CURLOPT_OPENSOCKETDATA(3)
• CURLOPT_CLOSESOCKETFUNCTION — callback for closing socket 🚪 see CURLOPT_CLOSESOCKETFUNCTION(3)
• CURLOPT_CLOSESOCKETDATA — data pointer to pass to the close socket callback 💅 see CURLOPT_CLOSESOCKETDATA(3)
• CURLOPT_PROGRESSFUNCTION — OBSOLETE callback for progress meter 💀 see CURLOPT_PROGRESSFUNCTION(3)
• CURLOPT_PROGRESSDATA — data pointer to pass to the progress meter callback 📊 see CURLOPT_PROGRESSDATA(3)
• CURLOPT_XFERINFOFUNCTION — callback for progress meter 🔥 see CURLOPT_XFERINFOFUNCTION(3)
• CURLOPT_XFERINFODATA — data pointer to pass to the progress meter callback 🌟 see CURLOPT_XFERINFODATA(3)
• CURLOPT_HEADERFUNCTION — callback for writing received headers 📨 see CURLOPT_HEADERFUNCTION(3)
• CURLOPT_HEADERDATA — data pointer to pass to the header callback 🎀 see CURLOPT_HEADERDATA(3)
• CURLOPT_DEBUGFUNCTION — callback for debug information 🐛 see CURLOPT_DEBUGFUNCTION(3)
• CURLOPT_DEBUGDATA — data pointer to pass to the debug callback 🔬 see CURLOPT_DEBUGDATA(3)
• CURLOPT_SSL_CTX_FUNCTION — callback for SSL context logic 🔐 see CURLOPT_SSL_CTX_FUNCTION(3)
• CURLOPT_SSL_CTX_DATA — data pointer to pass to the SSL context callback 🗝️ see CURLOPT_SSL_CTX_DATA(3)
• CURLOPT_CONV_TO_NETWORK_FUNCTION — callback for code base conversion 🔄 see CURLOPT_CONV_TO_NETWORK_FUNCTION(3)
• CURLOPT_CONV_FROM_NETWORK_FUNCTION — callback for code base conversion 🔁 see CURLOPT_CONV_FROM_NETWORK_FUNCTION(3)
• CURLOPT_CONV_FROM_UTF8_FUNCTION — callback for code base conversion 🈺 see CURLOPT_CONV_FROM_UTF8_FUNCTION(3)
• CURLOPT_INTERLEAVEFUNCTION — callback for RTSP interleaved data 🎬 see CURLOPT_INTERLEAVEFUNCTION(3)
• CURLOPT_INTERLEAVEDATA — data pointer to pass to the RTSP interleave callback 🍿 see CURLOPT_INTERLEAVEDATA(3)
• CURLOPT_CHUNK_BGN_FUNCTION — callback for wildcard download start of chunk 🧩 see CURLOPT_CHUNK_BGN_FUNCTION(3)
• CURLOPT_CHUNK_END_FUNCTION — callback for wildcard download end of chunk 🏁 see CURLOPT_CHUNK_END_FUNCTION(3)
• CURLOPT_CHUNK_DATA — data pointer to pass to the chunk callbacks 🎁 see CURLOPT_CHUNK_DATA(3)
• CURLOPT_FNMATCH_FUNCTION — callback for wildcard matching 🃏 see CURLOPT_FNMATCH_FUNCTION(3)
• CURLOPT_FNMATCH_DATA — data pointer to pass to the wildcard matching callback 🌸 see CURLOPT_FNMATCH_DATA(3)
• CURLOPT_SUPPRESS_CONNECT_HEADERS — suppress proxy CONNECT response headers from user callbacks 🤫 see CURLOPT_SUPPRESS_CONNECT_HEADERS(3)
• CURLOPT_RESOLVER_START_FUNCTION — callback to be called before a new resolve request is started 🚦 see CURLOPT_RESOLVER_START_FUNCTION(3)
• CURLOPT_RESOLVER_START_DATA — data pointer to pass to resolver start callback 🎀 see CURLOPT_RESOLVER_START_DATA(3)

---

😭 ERROR OPTIONS 😭

• CURLOPT_ERRORBUFFER — error message buffer 📝 see CURLOPT_ERRORBUFFER(3)
• CURLOPT_STDERR — stderr replacement stream 🖥️ see CURLOPT_STDERR(3)
• CURLOPT_FAILONERROR — fail on HTTP 4xx errors 💀 CURLOPT_FAILONERROR(3)
• CURLOPT_KEEP_SENDING_ON_ERROR — keep sending on HTTP >= 300 errors 🚀 CURLOPT_KEEP_SENDING_ON_ERROR(3)

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🌐 NETWORK OPTIONS 🌐

• CURLOPT_URL — URL to work on 🔗 see CURLOPT_URL(3)
• CURLOPT_PATH_AS_IS — disable squashing /../ and /./ sequences in the path 🛣️ see CURLOPT_PATH_AS_IS(3)
• CURLOPT_PROTOCOLS — allowed protocols ✅ see CURLOPT_PROTOCOLS(3)
• CURLOPT_REDIR_PROTOCOLS — protocols to allow redirects to ↩️ see CURLOPT_REDIR_PROTOCOLS(3)
• CURLOPT_DEFAULT_PROTOCOL — default protocol 🎯 see CURLOPT_DEFAULT_PROTOCOL(3)
• CURLOPT_PROXY — proxy to use 🕵️ see CURLOPT_PROXY(3)
• CURLOPT_PRE_PROXY — Socks proxy to use 🧦 see CURLOPT_PRE_PROXY(3)
• CURLOPT_PROXYPORT — proxy port to use 🔢 see CURLOPT_PROXYPORT(3)
• CURLOPT_PROXYTYPE — proxy type 🏷️ see CURLOPT_PROXYTYPE(3)
• CURLOPT_NOPROXY — filter out hosts from proxy use 🚫 CURLOPT_NOPROXY(3)
• CURLOPT_HTTPPROXYTUNNEL — tunnel through the HTTP proxy 🚇 CURLOPT_HTTPPROXYTUNNEL(3)
• CURLOPT_CONNECT_TO — connect to a specific host and port 📍 see CURLOPT_CONNECT_TO(3)
• CURLOPT_SOCKS5_AUTH — Socks5 authentication methods 🔑 see CURLOPT_SOCKS5_AUTH(3)
• CURLOPT_SOCKS5_GSSAPI_SERVICE — Socks5 GSSAPI service name 📛 CURLOPT_SOCKS5_GSSAPI_SERVICE(3)
• CURLOPT_SOCKS5_GSSAPI_NEC — Socks5 GSSAPI NEC mode 🧠 see CURLOPT_SOCKS5_GSSAPI_NEC(3)
• CURLOPT_PROXY_SERVICE_NAME — proxy authentication service name 🪪 CURLOPT_PROXY_SERVICE_NAME(3)
• CURLOPT_HAPROXYPROTOCOL — send an HAProxy PROXY protocol v1 header 📮 see CURLOPT_HAPROXYPROTOCOL(3)
• CURLOPT_SERVICE_NAME — authentication service name 🏷️ CURLOPT_SERVICE_NAME(3)
• CURLOPT_INTERFACE — bind connection locally to this 🪢 see CURLOPT_INTERFACE(3)
• CURLOPT_LOCALPORT — bind connection locally to this port 🔌 see CURLOPT_LOCALPORT(3)
• CURLOPT_LOCALPORTRANGE — bind connection locally to port range 📶 see CURLOPT_LOCALPORTRANGE(3)
• CURLOPT_DNS_CACHE_TIMEOUT — timeout for DNS cache ⏳ see CURLOPT_DNS_CACHE_TIMEOUT(3)
• CURLOPT_DNS_USE_GLOBAL_CACHE — OBSOLETE enable global DNS cache 💀 see CURLOPT_DNS_USE_GLOBAL_CACHE(3)
• CURLOPT_DOH_URL — use this DOH server for name resolves 🧭 see CURLOPT_DOH_URL(3)
• CURLOPT_BUFFERSIZE — ask for alternate buffer size 📦 see CURLOPT_BUFFERSIZE(3)
• CURLOPT_PORT — port number to connect to 🔢 see CURLOPT_PORT(3)
• CURLOPT_TCP_FASTOPEN — enable TFO, TCP Fast Open ⚡ see CURLOPT_TCP_FASTOPEN(3)
• CURLOPT_TCP_NODELAY — disable the Nagle algorithm 🐌 see CURLOPT_TCP_NODELAY(3)
• CURLOPT_ADDRESS_SCOPE — IPv6 scope for local addresses 🌍 see CURLOPT_ADDRESS_SCOPE(3)
• CURLOPT_TCP_KEEPALIVE — enable TCP keep-alive 💓 see CURLOPT_TCP_KEEPALIVE(3)
• CURLOPT_TCP_KEEPIDLE — idle time before sending keep-alive 😴 see CURLOPT_TCP_KEEPIDLE(3)
• CURLOPT_TCP_KEEPINTVL — interval between keep-alive probes ⏱️ see CURLOPT_TCP_KEEPINTVL(3)
• CURLOPT_UNIX_SOCKET_PATH — path to a Unix domain socket 🧵 see CURLOPT_UNIX_SOCKET_PATH(3)
• CURLOPT_ABSTRACT_UNIX_SOCKET — path to an abstract Unix domain socket 🌀 see CURLOPT_ABSTRACT_UNIX_SOCKET(3)

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okay that's this chunk done and there is so more coming 👀 don't go anywhere bestie 🫶

✨ NAMES and PASSWORDS OPTIONS (Authentication) ✨

okay bestie, this whole cluster is about who you are when you knock on the server's door 🔑 — usernames, passwords, tokens, the works. Every single one links off to its own page, so go deep whenever you need.

• CURLOPT_NETRC — turns on .netrc parsing. See CURLOPT_NETRC(3)
• CURLOPT_NETRC_FILE — picks which .netrc file name to use. See CURLOPT_NETRC_FILE(3)
• CURLOPT_USERPWD — your user name and password. See CURLOPT_USERPWD(3)
• CURLOPT_PROXYUSERPWD — the proxy's user name and password. See CURLOPT_PROXYUSERPWD(3)
• CURLOPT_USERNAME — just the user name, no password energy. See CURLOPT_USERNAME(3)
• CURLOPT_PASSWORD — just the password. See CURLOPT_PASSWORD(3)
• CURLOPT_LOGIN_OPTIONS — login options. See CURLOPT_LOGIN_OPTIONS(3)
• CURLOPT_PROXYUSERNAME — proxy user name. See CURLOPT_PROXYUSERNAME(3)
• CURLOPT_PROXYPASSWORD — proxy password. See CURLOPT_PROXYPASSWORD(3)
• CURLOPT_HTTPAUTH — which HTTP server authentication methods you're willing to do. See CURLOPT_HTTPAUTH(3)
• CURLOPT_TLSAUTH_USERNAME — TLS authentication user name. See CURLOPT_TLSAUTH_USERNAME(3)
• CURLOPT_PROXY_TLSAUTH_USERNAME — proxy TLS authentication user name. See CURLOPT_PROXY_TLSAUTH_USERNAME(3)
• CURLOPT_TLSAUTH_PASSWORD — TLS authentication password. See CURLOPT_TLSAUTH_PASSWORD(3)
• CURLOPT_PROXY_TLSAUTH_PASSWORD — proxy TLS authentication password. See CURLOPT_PROXY_TLSAUTH_PASSWORD(3)
• CURLOPT_TLSAUTH_TYPE — TLS authentication methods. See CURLOPT_TLSAUTH_TYPE(3)
• CURLOPT_PROXY_TLSAUTH_TYPE — proxy TLS authentication methods. See CURLOPT_PROXY_TLSAUTH_TYPE(3)
• CURLOPT_PROXYAUTH — HTTP proxy authentication methods. See CURLOPT_PROXYAUTH(3)
• CURLOPT_SASL_AUTHZID — the SASL authorisation identity, aka the identity you want to act as. See CURLOPT_SASL_AUTHZID(3)
• CURLOPT_SASL_IR — enables SASL initial response. See CURLOPT_SASL_IR(3)
• CURLOPT_XOAUTH2_BEARER — your OAuth2 bearer token 🎟️. See CURLOPT_XOAUTH2_BEARER(3)
• CURLOPT_DISALLOW_USERNAME_IN_URL — nope, no username allowed in the URL. See CURLOPT_DISALLOW_USERNAME_IN_URL(3)

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🌐 HTTP OPTIONS

this is the big one, the main character section 💅 — headers, redirects, cookies, HTTP/2 streams, all of it. Settle in.

• CURLOPT_AUTOREFERER — automatically sets the Referer: header. See CURLOPT_AUTOREFERER(3)
• CURLOPT_ACCEPT_ENCODING — sets Accept-Encoding and decompresses the data for you automatically. See CURLOPT_ACCEPT_ENCODING(3)
• CURLOPT_TRANSFER_ENCODING — asks for Transfer-Encoding. See CURLOPT_TRANSFER_ENCODING(3)
• CURLOPT_FOLLOWLOCATION — follows those HTTP redirects like the loyal bestie it is. See CURLOPT_FOLLOWLOCATION(3)
• CURLOPT_UNRESTRICTED_AUTH — stops restricting authentication to the original host. See CURLOPT_UNRESTRICTED_AUTH(3)
• CURLOPT_MAXREDIRS — the max number of redirects to follow before it says "enough". See CURLOPT_MAXREDIRS(3)
• CURLOPT_POSTREDIR — how to act on redirects after a POST. See CURLOPT_POSTREDIR(3)
• CURLOPT_PUT — issues an HTTP PUT request. See CURLOPT_PUT(3)
• CURLOPT_POST — issues an HTTP POST request. See CURLOPT_POST(3)
• CURLOPT_POSTFIELDS — sends a POST with this data. See CURLOPT_POSTFIELDS(3)
• CURLOPT_POSTFIELDSIZE — tells it the POST data is this big. See CURLOPT_POSTFIELDSIZE(3)
• CURLOPT_POSTFIELDSIZE_LARGE — same vibe, also tells it the POST data is this big. See CURLOPT_POSTFIELDSIZE_LARGE(3)
• CURLOPT_COPYPOSTFIELDS — sends a POST with this data and copies it. See CURLOPT_COPYPOSTFIELDS(3)
• CURLOPT_HTTPPOST — multipart formpost HTTP POST. See CURLOPT_HTTPPOST(3)
• CURLOPT_REFERER — the Referer: header. See CURLOPT_REFERER(3)
• CURLOPT_USERAGENT — the User-Agent: header. See CURLOPT_USERAGENT(3)
• CURLOPT_HTTPHEADER — your own custom HTTP headers 🎀. See CURLOPT_HTTPHEADER(3)
• CURLOPT_HEADEROPT — controls those custom headers. See CURLOPT_HEADEROPT(3)
• CURLOPT_PROXYHEADER — custom HTTP headers sent to the proxy. See CURLOPT_PROXYHEADER(3)
• CURLOPT_HTTP200ALIASES — alternative versions of 200 OK. See CURLOPT_HTTP200ALIASES(3)
• CURLOPT_COOKIE — the cookie(s) to send 🍪. See CURLOPT_COOKIE(3)
• CURLOPT_COOKIEFILE — the file to read cookies from. See CURLOPT_COOKIEFILE(3)
• CURLOPT_COOKIEJAR — the file to write cookies to. See CURLOPT_COOKIEJAR(3)
• CURLOPT_COOKIESESSION — starts a brand new cookie session. See CURLOPT_COOKIESESSION(3)
• CURLOPT_COOKIELIST — adds or controls cookies. See CURLOPT_COOKIELIST(3)
• CURLOPT_ALTSVC — specifies the Alt-Svc: cache file name. See CURLOPT_ALTSVC(3)
• CURLOPT_ALTSVC_CTRL — enables and configures Alt-Svc: treatment. See CURLOPT_ALTSVC_CTRL(3)
• CURLOPT_HTTPGET — does an HTTP GET request. See CURLOPT_HTTPGET(3)
• CURLOPT_REQUEST_TARGET — sets the request target. See CURLOPT_REQUEST_TARGET(3)
• CURLOPT_HTTP_VERSION — which HTTP version to use. See CURLOPT_HTTP_VERSION(3)
• CURLOPT_HTTP09_ALLOWED — allows HTTP/0.9 responses (yes, that fossil). See CURLOPT_HTTP09_ALLOWED(3)
• CURLOPT_IGNORE_CONTENT_LENGTH — ignores Content-Length. See CURLOPT_IGNORE_CONTENT_LENGTH(3)
• CURLOPT_HTTP_CONTENT_DECODING — disables Content decoding. See CURLOPT_HTTP_CONTENT_DECODING(3)
• CURLOPT_HTTP_TRANSFER_DECODING — disables Transfer decoding. See CURLOPT_HTTP_TRANSFER_DECODING(3)
• CURLOPT_EXPECT_100_TIMEOUT_MS — the 100-continue timeout. See CURLOPT_EXPECT_100_TIMEOUT_MS(3)
• CURLOPT_TRAILERFUNCTION — sets the callback for sending trailing headers. See CURLOPT_TRAILERFUNCTION(3)
• CURLOPT_TRAILERDATA — a custom pointer passed to that trailing headers callback. See CURLOPT_TRAILERDATA(3)
• CURLOPT_PIPEWAIT — waits on the connection so it can pipeline on it. See CURLOPT_PIPEWAIT(3)
• CURLOPT_STREAM_DEPENDS — this HTTP/2 stream depends on another one. See CURLOPT_STREAM_DEPENDS(3)
• CURLOPT_STREAM_DEPENDS_E — this HTTP/2 stream depends on another one exclusively. See CURLOPT_STREAM_DEPENDS_E(3)
• CURLOPT_STREAM_WEIGHT — sets this HTTP/2 stream's weight ⚖️. See CURLOPT_STREAM_WEIGHT(3)

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📧 SMTP OPTIONS

mail girlies rise 🫶 — who's sending, who's receiving, and who's authenticating.

• CURLOPT_MAIL_FROM — the address of the sender. See CURLOPT_MAIL_FROM(3)
• CURLOPT_MAIL_RCPT — the address(es) of the recipients. See CURLOPT_MAIL_RCPT(3)
• CURLOPT_MAIL_AUTH — the authentication address. See CURLOPT_MAIL_AUTH(3)
• CURLOPT_MAIL_RCPT_ALLLOWFAILS — allows the RCPT TO command to fail for some recipients. See CURLOPT_MAIL_RCPT_ALLLOWFAILS(3)

💀 just so you know, that triple-L spelling (ALLLOWFAILS) is literally how it's spelled in the option name. not a typo of mine, bestie — copy it exactly.

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📦 TFTP OPTIONS

tiny but mighty, two options, both iconic in their own lowkey way.

• CURLOPT_TFTP_BLKSIZE — the TFTP block size. See CURLOPT_TFTP_BLKSIZE(3)
• CURLOPT_TFTP_NO_OPTIONS — does not send TFTP options requests. See CURLOPT_TFTP_NO_OPTIONS(3)

---

🗂️ FTP OPTIONS

the vintage queen of protocols and honestly she still serves 👑. Here's every knob.

• CURLOPT_FTPPORT — use active FTP. See CURLOPT_FTPPORT(3)
• CURLOPT_QUOTE — commands to run before transfer. See CURLOPT_QUOTE(3)
• CURLOPT_POSTQUOTE — commands to run after transfer. See CURLOPT_POSTQUOTE(3)
• CURLOPT_PREQUOTE — commands to run just before transfer. See CURLOPT_PREQUOTE(3)
• CURLOPT_APPEND — appends to the remote file. See CURLOPT_APPEND(3)
• CURLOPT_FTP_USE_EPRT — use EPTR. See CURLOPT_FTP_USE_EPRT(3)
• CURLOPT_FTP_USE_EPSV — use EPSV. See CURLOPT_FTP_USE_EPSV(3)
• CURLOPT_FTP_USE_PRET — use PRET. See CURLOPT_FTP_USE_PRET(3)
• CURLOPT_FTP_CREATE_MISSING_DIRS — creates missing directories on the remote server. See CURLOPT_FTP_CREATE_MISSING_DIRS(3)
• CURLOPT_FTP_RESPONSE_TIMEOUT — the timeout for FTP responses. See CURLOPT_FTP_RESPONSE_TIMEOUT(3)
• CURLOPT_FTP_ALTERNATIVE_TO_USER — an alternative to USER. See CURLOPT_FTP_ALTERNATIVE_TO_USER(3)
• CURLOPT_FTP_SKIP_PASV_IP — ignores the IP address in the PASV response. See CURLOPT_FTP_SKIP_PASV_IP(3)
• CURLOPT_FTPSSLAUTH — controls how to do TLS. See CURLOPT_FTPSSLAUTH(3)
• CURLOPT_FTP_SSL_CCC — goes back to non-TLS again after authentication. See CURLOPT_FTP_SSL_CCC(3)
• CURLOPT_FTP_ACCOUNT — sends the ACCT command. See CURLOPT_FTP_ACCOUNT(3)
• CURLOPT_FTP_FILEMETHOD — specifies how to reach files. See CURLOPT_FTP_FILEMETHOD(3)

---

🎬 RTSP OPTIONS

streaming protocol hours 🌈 — sessions, sequence numbers, and transport headers.

• CURLOPT_RTSP_REQUEST — the RTSP request. See CURLOPT_RTSP_REQUEST(3)
• CURLOPT_RTSP_SESSION_ID — the RTSP session-id. See CURLOPT_RTSP_SESSION_ID(3)
• CURLOPT_RTSP_STREAM_URI — the RTSP stream URI. See CURLOPT_RTSP_STREAM_URI(3)
• CURLOPT_RTSP_TRANSPORT — the RTSP Transport: header. See CURLOPT_RTSP_TRANSPORT(3)
• CURLOPT_RTSP_CLIENT_CSEQ — the client CSEQ number. See CURLOPT_RTSP_CLIENT_CSEQ(3)
• CURLOPT_RTSP_SERVER_CSEQ — the CSEQ number for RTSP Server->Client request. See CURLOPT_RTSP_SERVER_CSEQ(3)

---

🧚 PROTOCOL OPTIONS

the general-purpose toolbox — stuff that works across protocols and doesn't want to be boxed in. very main character energy, honestly.

• CURLOPT_TRANSFERTEXT — uses text transfer. See CURLOPT_TRANSFERTEXT(3)
• CURLOPT_PROXY_TRANSFER_MODE — adds the transfer mode to the URL over a proxy. See CURLOPT_PROXY_TRANSFER_MODE(3)
• CURLOPT_CRLF — converts newlines. See CURLOPT_CRLF(3)
• CURLOPT_RANGE — range requests, for when you only want part of the thing. See CURLOPT_RANGE(3)
• CURLOPT_RESUME_FROM — resumes a transfer. See CURLOPT_RESUME_FROM(3)
• CURLOPT_RESUME_FROM_LARGE — also resumes a transfer. See CURLOPT_RESUME_FROM_LARGE(3)
• CURLOPT_CURLU — sets the URL to work on with CURLU *. See CURLOPT_CURLU(3)
• CURLOPT_CUSTOMREQUEST — a custom request/method. See CURLOPT_CUSTOMREQUEST(3)
• CURLOPT_FILETIME — requests the file modification date and time 🕰️. See CURLOPT_FILETIME(3)
• CURLOPT_DIRLISTONLY — list only. See CURLOPT_DIRLISTONLY(3)
• CURLOPT_NOBODY — do not get the body contents. See CURLOPT_NOBODY(3)
• CURLOPT_INFILESIZE — the size of the file to send. See CURLOPT_INFILESIZE(3)
• CURLOPT_INFILESIZE_LARGE — the size of the file to send. See CURLOPT_INFILESIZE_LARGE(3)
• CURLOPT_UPLOAD — uploads data. See CURLOPT_UPLOAD(3)
• CURLOPT_UPLOAD_BUFFERSIZE — sets the upload buffer size. See CURLOPT_UPLOAD_BUFFERSIZE(3)
• CURLOPT_MIMEPOST — posts/sends MIME data. See CURLOPT_MIMEPOST(3)
• CURLOPT_MAXFILESIZE — the maximum file size to get. See CURLOPT_MAXFILESIZE(3)
• CURLOPT_MAXFILESIZE_LARGE — the maximum file size to get. See CURLOPT_MAXFILESIZE_LARGE(3)
• CURLOPT_TIMECONDITION — makes a time conditional request. See CURLOPT_TIMECONDITION(3)
• CURLOPT_TIMEVALUE — the time value for that time conditional request. See CURLOPT_TIMEVALUE(3)
• CURLOPT_TIMEVALUE_LARGE — the time value for that time conditional request. See CURLOPT_TIMEVALUE_LARGE(3)

🔌 CONNECTION OPTIONS 🔌

okay so these are the ones that decide like, how your little client actually reaches out and touches the server. connection era 💅

• CURLOPT_TIMEOUT — how long the entire request is allowed to take, start to finish. See CURLOPT_TIMEOUT(3)
• CURLOPT_TIMEOUT_MS — same energy, but measured in milliseconds. See CURLOPT_TIMEOUT_MS(3)
• CURLOPT_LOW_SPEED_LIMIT — the low-speed threshold that'll abort a transfer if it's crawling. See CURLOPT_LOW_SPEED_LIMIT(3)
• CURLOPT_LOW_SPEED_TIME — how long you're willing to stay below that speed before the abort kicks in. See CURLOPT_LOW_SPEED_TIME(3)
• CURLOPT_MAX_SEND_SPEED_LARGE — caps your upload speed right there. See CURLOPT_MAX_SEND_SPEED_LARGE(3)
• CURLOPT_MAX_RECV_SPEED_LARGE — caps your download speed, same deal. See CURLOPT_MAX_RECV_SPEED_LARGE(3)
• CURLOPT_MAXCONNECTS — the max number of connections chilling in the connection pool. See CURLOPT_MAXCONNECTS(3)
• CURLOPT_FRESH_CONNECT — bestie, get a brand new connection, don't recycle. CURLOPT_FRESH_CONNECT(3)
• CURLOPT_FORBID_REUSE — blocks any later connections from re-using this one. See CURLOPT_FORBID_REUSE(3)
• CURLOPT_MAXAGE_CONN — puts an age limit on connections that are eligible for reuse. See CURLOPT_MAXAGE_CONN(3)
• CURLOPT_CONNECTTIMEOUT — timeout for just the connection phase, not the whole thing. See CURLOPT_CONNECTTIMEOUT(3)
• CURLOPT_CONNECTTIMEOUT_MS — connection phase timeout, but in milliseconds obviously. See CURLOPT_CONNECTTIMEOUT_MS(3)
• CURLOPT_IPRESOLVE — which IP version to resolve to. See CURLOPT_IPRESOLVE(3)
• CURLOPT_CONNECT_ONLY — connect and that's it, nothing else happens. See CURLOPT_CONNECT_ONLY(3)
• CURLOPT_USE_SSL — turns on TLS/SSL. See CURLOPT_USE_SSL(3)
• CURLOPT_RESOLVE — hand it fixed/fake name resolves, your own little DNS fantasy. See CURLOPT_RESOLVE(3)
• CURLOPT_DNS_INTERFACE — binds name resolves to this interface. See CURLOPT_DNS_INTERFACE(3)
• CURLOPT_DNS_LOCAL_IP4 — binds name resolves to this IP4 address. See CURLOPT_DNS_LOCAL_IP4(3)
• CURLOPT_DNS_LOCAL_IP6 — binds name resolves to this IP6 address. See CURLOPT_DNS_LOCAL_IP6(3)
• CURLOPT_DNS_SERVERS — your preferred DNS servers, like a fave list. See CURLOPT_DNS_SERVERS(3)
• CURLOPT_DNS_SHUFFLE_ADDRESSES — shuffles the addresses before using them 🎲 See CURLOPT_DNS_SHUFFLE_ADDRESSES(3)
• CURLOPT_ACCEPTTIMEOUT_MS — how long you'll wait for the server's connect-back to be accepted. See CURLOPT_ACCEPTTIMEOUT_MS(3)
• CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS — the timeout for happy eyeballs 🥺👀 See CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS(3)
• CURLOPT_UPKEEP_INTERVAL_MS — sets the interval at which connection upkeep gets performed. See CURLOPT_UPKEEP_INTERVAL_MS(3)

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🔐 SSL and SECURITY OPTIONS 🔐

this whole section is the certified-locked-down-girl era. certs, keys, ciphers, the works ✨

• CURLOPT_SSLCERT — the client cert. See CURLOPT_SSLCERT(3)
• CURLOPT_SSLCERT_BLOB — client cert, but as a memory buffer. See CURLOPT_SSLCERT_BLOB(3)
• CURLOPT_PROXY_SSLCERT — the proxy's client cert. See CURLOPT_PROXY_SSLCERT(3)
• CURLOPT_PROXY_SSLCERT_BLOB — proxy client cert as a memory buffer. See CURLOPT_PROXY_SSLCERT_BLOB(3)
• CURLOPT_SSLCERTTYPE — tells it the client cert type. See CURLOPT_SSLCERTTYPE(3)
• CURLOPT_PROXY_SSLCERTTYPE — the proxy client cert type. See CURLOPT_PROXY_SSLCERTTYPE(3)
• CURLOPT_SSLKEY — the client key. See CURLOPT_SSLKEY(3)
• CURLOPT_SSLKEY_BLOB — client key, memory-buffer style. See CURLOPT_SSLKEY_BLOB(3)
• CURLOPT_PROXY_SSLKEY — the proxy client key. See CURLOPT_PROXY_SSLKEY(3)
• CURLOPT_PROXY_SSLKEY_BLOB — proxy client key (yes, the man page literally just says that again 😭). See CURLOPT_PROXY_SSLKEY_BLOB(3)
• CURLOPT_SSLKEYTYPE — client key type. See CURLOPT_SSLKEYTYPE(3)
• CURLOPT_PROXY_SSLKEYTYPE — proxy client key type. See CURLOPT_PROXY_SSLKEYTYPE(3)
• CURLOPT_KEYPASSWD — the password for the client key 🤫 See CURLOPT_KEYPASSWD(3)
• CURLOPT_PROXY_KEYPASSWD — password for the proxy's client key. See CURLOPT_PROXY_KEYPASSWD(3)
• CURLOPT_SSL_ENABLE_ALPN — lets it use ALPN. See CURLOPT_SSL_ENABLE_ALPN(3)
• CURLOPT_SSL_ENABLE_NPN — lets it use NPN. See CURLOPT_SSL_ENABLE_NPN(3)
• CURLOPT_SSLENGINE — uses this identifier with the SSL engine. See CURLOPT_SSLENGINE(3)
• CURLOPT_SSLENGINE_DEFAULT — the default SSL engine, no identifier needed. See CURLOPT_SSLENGINE_DEFAULT(3)
• CURLOPT_SSL_FALSESTART — turns on TLS False Start. See CURLOPT_SSL_FALSESTART(3)
• CURLOPT_SSLVERSION — which SSL version to use. See CURLOPT_SSLVERSION(3)
• CURLOPT_PROXY_SSLVERSION — which SSL version to use for the proxy. See CURLOPT_PROXY_SSLVERSION(3)
• CURLOPT_SSL_VERIFYHOST — checks the host name inside the SSL certificate. See CURLOPT_SSL_VERIFYHOST(3)
• CURLOPT_PROXY_SSL_VERIFYHOST — checks the host name in the proxy's SSL certificate. See CURLOPT_PROXY_SSL_VERIFYHOST(3)
• CURLOPT_SSL_VERIFYPEER — verifies the SSL certificate itself. See CURLOPT_SSL_VERIFYPEER(3)
• CURLOPT_PROXY_SSL_VERIFYPEER — verifies the proxy's SSL certificate. See CURLOPT_PROXY_SSL_VERIFYPEER(3)
• CURLOPT_SSL_VERIFYSTATUS — verifies the status of the SSL certificate. See CURLOPT_SSL_VERIFYSTATUS(3)
• CURLOPT_CAINFO — the CA cert bundle. See CURLOPT_CAINFO(3)
• CURLOPT_PROXY_CAINFO — the CA cert bundle for the proxy. See CURLOPT_PROXY_CAINFO(3)
• CURLOPT_ISSUERCERT — the issuer certificate. See CURLOPT_ISSUERCERT(3)
• CURLOPT_ISSUERCERT_BLOB — issuer certificate as a memory buffer. See CURLOPT_ISSUERCERT_BLOB(3)
• CURLOPT_PROXY_ISSUERCERT — the proxy's issuer certificate. See CURLOPT_PROXY_ISSUERCERT(3)
• CURLOPT_PROXY_ISSUERCERT_BLOB — proxy issuer certificate as a memory buffer. See CURLOPT_PROXY_ISSUERCERT_BLOB(3)
• CURLOPT_CAPATH — the path to the CA cert bundle. See CURLOPT_CAPATH(3)
• CURLOPT_PROXY_CAPATH — the path to the proxy's CA cert bundle. See CURLOPT_PROXY_CAPATH(3)
• CURLOPT_CRLFILE — the Certificate Revocation List. See CURLOPT_CRLFILE(3)
• CURLOPT_PROXY_CRLFILE — the proxy's Certificate Revocation List. See CURLOPT_PROXY_CRLFILE(3)
• CURLOPT_CERTINFO — extracts certificate info. See CURLOPT_CERTINFO(3)
• CURLOPT_PINNEDPUBLICKEY — sets the pinned SSL public key. See CURLOPT_PINNEDPUBLICKEY(3)
• CURLOPT_PROXY_PINNEDPUBLICKEY — sets the proxy's pinned SSL public key. See CURLOPT_PROXY_PINNEDPUBLICKEY(3)
• CURLOPT_RANDOM_FILE — gives it a source for entropy random data. See CURLOPT_RANDOM_FILE(3)
• CURLOPT_EGDSOCKET — points out the EGD socket for entropy. See CURLOPT_EGDSOCKET(3)
• CURLOPT_SSL_CIPHER_LIST — which ciphers to use. See CURLOPT_SSL_CIPHER_LIST(3)
• CURLOPT_PROXY_SSL_CIPHER_LIST — which ciphers to use for the proxy. See CURLOPT_PROXY_SSL_CIPHER_LIST(3)
• CURLOPT_TLS13_CIPHERS — which TLS 1.3 cipher suites to use. See CURLOPT_TLS13_CIPHERS(3)
• CURLOPT_PROXY_TLS13_CIPHERS — which TLS 1.3 cipher suites to use for the proxy. See CURLOPT_PROXY_TLS13_CIPHERS(3)
• CURLOPT_SSL_SESSIONID_CACHE — disables the SSL session-id cache. See CURLOPT_SSL_SESSIONID_CACHE(3)
• CURLOPT_SSL_OPTIONS — controls SSL behavior. See CURLOPT_SSL_OPTIONS(3)
• CURLOPT_PROXY_SSL_OPTIONS — controls proxy SSL behavior. See CURLOPT_PROXY_SSL_OPTIONS(3)
• CURLOPT_KRBLEVEL — the Kerberos security level. See CURLOPT_KRBLEVEL(3)
• CURLOPT_GSSAPI_DELEGATION — disables GSS-API delegation. See CURLOPT_GSSAPI_DELEGATION(3)

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🐚 SSH OPTIONS 🐚

for when you're doing the secure-shell thing. keys and known hosts and all that good stuff 🗝️

• CURLOPT_SSH_AUTH_TYPES — which SSH authentication types to allow. See CURLOPT_SSH_AUTH_TYPES(3)
• CURLOPT_SSH_COMPRESSION — turns SSH compression on. See CURLOPT_SSH_COMPRESSION(3)
• CURLOPT_SSH_HOST_PUBLIC_KEY_MD5 — the MD5 of the host's public key. See CURLOPT_SSH_HOST_PUBLIC_KEY_MD5(3)
• CURLOPT_SSH_PUBLIC_KEYFILE — file name of the public key. See CURLOPT_SSH_PUBLIC_KEYFILE(3)
• CURLOPT_SSH_PRIVATE_KEYFILE — file name of the private key (protect her 🫶). See CURLOPT_SSH_PRIVATE_KEYFILE(3)
• CURLOPT_SSH_KNOWNHOSTS — file name that holds the known hosts. See CURLOPT_SSH_KNOWNHOSTS(3)
• CURLOPT_SSH_KEYFUNCTION — the callback for known-hosts handling. See CURLOPT_SSH_KEYFUNCTION(3)
• CURLOPT_SSH_KEYDATA — a custom pointer to pass along to the ssh key callback. See CURLOPT_SSH_KEYDATA(3)

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🎀 OTHER OPTIONS 🎀

the little grab-bag section, love her 💖

• CURLOPT_PRIVATE — a private pointer for you to store stuff in. See CURLOPT_PRIVATE(3)
• CURLOPT_SHARE — the share object to use. See CURLOPT_SHARE(3)
• CURLOPT_NEW_FILE_PERMS — the mode used when creating new remote files. See CURLOPT_NEW_FILE_PERMS(3)
• CURLOPT_NEW_DIRECTORY_PERMS — the mode used when creating new remote directories. See CURLOPT_NEW_DIRECTORY_PERMS(3)

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📟 TELNET OPTIONS 📟

one singular option. she's lowkey iconic for standing alone 😌

• CURLOPT_TELNETOPTIONS — the TELNET options. See CURLOPT_TELNETOPTIONS(3)

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🌈 RETURN VALUE 🌈

CURLE_OK (which is zero) means the option was set properly 💚. Anything non-zero means an error happened, exactly as <gnurl/curl.h> defines it. Want the full list with descriptions? Go read libcurl-errors(3), it's all laid out there.

🚨 Important bestie PSA: any strings you pass in to libcurl must be shorter than 8000000 bytes. If they're not, curl_easy_setopt(3) returns CURLE_BAD_FUNCTION_ARGUMENT (this was added in 7.65.0, so don't come for older versions about it).

If you try to set an option libcurl genuinely doesn't know about — maybe your library is too old to support it, or the option got removed in a recent version — the function returns CURLE_UNKNOWN_OPTION. And if support for that option was disabled at compile-time, it returns CURLE_NOT_BUILT_IN. No cap, those are two different errors 😭

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✨ EXAMPLE ✨

the little hello-world of curl, we love to see it:

CURL *curl = curl_easy_init();
if(curl) {
  CURLcode res;
  curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
  res = curl_easy_perform(curl);
  curl_easy_cleanup(curl);
}

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👀 SEE ALSO 👀

go read these next, iykyk:

curl_easy_init(3), curl_easy_cleanup(3), curl_easy_reset(3), curl_easy_getinfo(3), curl_multi_setopt(3)

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and that's the whole page, bestie!! 🎀 you just read the entire gnurl_easy_setopt(3) man page — every last option, every last "See ...(3)". this gorgeous thing ships as libcurl 7.38.0, dated 25 Jun 2014, and it lives at gnurl_easy_setopt(3). go forth and set some options 💅✨