[#ERR_error_string]
= ERR_error_string
:mrdocs:

Format a human‐readable description of error code `e` into a buffer.

== Synopsis

Declared in `<openssl/err.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
char*
ERR_error_string(
    unsigned long e,
    char* buf);
----

== Return Value

Pointer to `buf,` or to the static buffer when `buf` is NULL.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *e*
| Packed error code from ERR_get_error() or similar.
| *buf*
| Destination buffer of at least 256 bytes, or NULL to use a static buffer (not thread‐safe).
|===


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