ERR_ERROR_STRING(3)

💖 ERR_ERROR_STRING(3) 💖

okay bestie, so this is from the Library Functions Manual — it's all about grabbing human-readable OpenSSL error messages and making sense of those cursed error codes 💅

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✨ NAME ✨

So like, the whole squad is here: ERR_error_string, ERR_error_string_n, ERR_lib_error_string, ERR_func_error_string, and ERR_reason_error_string — they all exist to obtain human-readable OpenSSL error messages 🫶

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🌸 SYNOPSIS 🌸

library “libcrypto” #include <openssl/err.h>

char *
ERR_error_string(unsigned long e, char *buf);

void
ERR_error_string_n(unsigned long e, char *buf, size_t len);

const char *
ERR_lib_error_string(unsigned long e);

const char *
ERR_func_error_string(unsigned long e);

const char *
ERR_reason_error_string(unsigned long e);

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🎀 DESCRIPTION 🎀

okay so ERR_error_string() generates a human-readable string representing the error code e and places it in buf. and like, buf must be at least 256 bytes long, no cap. if buf is NULL, the error string gets placed in a static buffer instead. but bestie… ⚠️ this function is not thread-safe and does no checks on the size of the buffer. so literally use ERR_error_string_n() instead, i'm begging 🥺

ERR_error_string_n() is the glow-up variant of ERR_error_string() that writes at most len characters (including the terminating NUL) and truncates the string if necessary. for ERR_error_string_n(), buf may not be NULL, periodt.

the string will have this format, iconic:

error:[error code]:[library name]:[function name]:[reason string]

the error code is an 8-digit hexadecimal number ✨ the library name, the function name, and the reason string are ASCII text.

ERR_lib_error_string(), ERR_func_error_string(), and ERR_reason_error_string() return the library name, the function name, and the reason string, respectively 💖

the OpenSSL error strings should be loaded by calling ERR_load_crypto_strings(3) or, for SSL applications, SSL_load_error_strings(3) first. if there is no text string registered for the given error code, the error string will contain the numeric code. lowkey tragic but that's the vibe check 🌈

ERR_print_errors(3) can be used to print all error codes currently in the queue — super handy, iykyk 🦋

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👑 RETURN VALUES 👑

ERR_error_string() returns a pointer to a static buffer containing the string if buf is NULL, or buf otherwise. slay.

ERR_lib_error_string(), ERR_func_error_string(), and ERR_reason_error_string() return the strings, or NULL if none is registered for the error code ✨

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💅 SEE ALSO 💅

ERR(3), ERR_get_error(3), ERR_load_crypto_strings(3), ERR_print_errors(3), SSL_load_error_strings(3)

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🦋 HISTORY 🦋

ERR_error_string(), ERR_lib_error_string(), ERR_func_error_string(), and ERR_reason_error_string() first appeared in SSLeay 0.4.4 and have been available since OpenBSD 2.4 — literal icons of longevity 💖

ERR_error_string_n() first appeared in OpenSSL 0.9.6 and has been available since OpenBSD 2.9 🌸

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okay that's the whole page bestie, you're gonna do amazing with these error strings, fr fr 🫶

Debian 🌈 June 8, 2025 🌈 ERR_ERROR_STRING(3) — mwah, go slay those error codes 💅✨