REALHOSTNAME(3)

🦋 realhostname(3) — LOCAL manual energy 🦋

okay so the header is being a little mysterious with UNTITLED(), but bestie, this is realhostname(3) from the LOCAL manual, and we are getting into it. 💅

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✨ NAME ✨

realhostname — convert an IP number to the real host name 💖

📚 LIBRARY 📚

System Utilities Library (libutil, -lutil) — yes, that one, periodt. 🎀

🌸 SYNOPSIS 🌸

#include <sys/types.h>
#include <netinet/in.h>
#include <libutil.h>

int
realhostname(char *host, size_t hsize, const struct in_addr *ip);

💫 DESCRIPTION 💫

okay so realhostname() converts ip to the corresponding host name. The way it does this: it resolves ip to a host name, then makes sure that host name resolves back to ip — both directions or it does not count, no cap. 🫶

host must point to a buffer of at least hsize bytes, and it will always be written to by this function. always always. 💅

If the name resolution does not work both ways, or if the host name is longer than hsize bytes, inet_ntoa(3) is used to convert ip to an ASCII form. fallback slay. ✨

⚠️ heads up bestie: if the string written to host is hsize bytes long, host will not be NUL terminated. that is the whole warning, and it matters. 😭

🎀 RETURN VALUES 🎀

The realhostname() function will return one of the following constants, which are defined in <libutil.h>:

• HOSTNAME_FOUND — a valid host name was found. iconic. ✨
• HOSTNAME_INCORRECTNAME — a host name was found, but it did not resolve back to the passed ip. host now contains the numeric value of ip. rude but okay. 💀
• HOSTNAME_INVALIDADDR — ip could not be resolved. host now contains the numeric value of ip. 🫠
• HOSTNAME_INVALIDNAME — a host name was found, but it could not be resolved back to any ip number. host now contains the numeric value of ip. the drama. 😭

🔗 SEE ALSO 🔗

• gethostbyaddr(3)
• gethostbyname(3)
• inet_ntoa(3)
• realhostname_sa(3)

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okay bye bestie 💖 this page’s footer energy is Debian, dated April 6, 1999 — vintage, honestly. 🎀✨