KHTTP_URLABS(3) Library Functions Manual KHTTP_URLABS(3)

khttp_urlabs, khttp_vurlabsURL formatting for kcgi

library “libkcgi”

#include <sys/types.h>
#include <stdarg.h>
#include <stdint.h>
#include <kcgi.h>

char *
khttp_urlabs(enum kscheme scheme, const char *host, uint16_t port, const char *path, ...);

char *
khttp_vurlabs(enum kscheme scheme, const char *host, uint16_t port, const char *path, va_list ap);

Format an absolute (full) URL. The host is in some standards called the "authority".


Passing a NULL or empty host will omit the "//", host, port component.

If the host is non-empty and not NULL and the path is also non-empty and not NULL, the path is prepended with a mandatory slash.

If the port is zero, it is omitted. The port is only used if host is non-empty and not NULL.

The variable arguments are arranged in pairs terminated by a single NULL. The first of each pair is the query string key, the second is the value. Both are char *. A NULL query string value is rendered as an empty string.

Only the query string pairs are URL-encoded, so the caller must make sure that the characters in host and path are valid.

The deprecated form of these functions, (), should no longer be used.

Return newly-allocated strings that must be freed with free(3) or NULL if allocation fails.

To print a full URL:

khttp_urlabs(KSCHEME_HTTPS,, 80, b, c, d, NULL);

This assigns

Setting the port to zero eliminates the port:

khttp_urlabs(KSCHEME_HTTPS,, 0, b, c, d, NULL);

This assigns

An empty path component ends with the domain (or query string).

khttp_urlabs(KSCHEME_HTTPS,, 0, , c, d, NULL);

This assigns

To use a host-less scheme, specify a NULL or empty host:

khttp_urlabs(KSCHEME_MAILTO, NULL, 0,, NULL);

This assigns

Written by Kristaps Dzonsons <>.

These functions can currently be used to create semantically invalid URLs such as https:?foo=bar by omitting components required for the scheme. Semantically-correct URLs are the responsibility of the caller. This behaviour may be verified for correctness in later versions of the software.

December 2, 2023 OpenBSD 7.4