X509_NAME_get_index_by_NID, X509_NAME_get_index_by_OBJ, X509_NAME_get_entry, X509_NAME_entry_count,

       Copyright 2002-2021 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use this file except in compliance
       with the License.  You can obtain a copy in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.

3.5.0                                              2025-06-04                   X509_NAME_GET_INDEX_BY_NID(3SSL)

       These functions allow an X509_NAME structure to be examined. The X509_NAME structure is the same as the
       Name type defined in RFC2459 (and elsewhere) and used for example in certificate subject and issuer
       names.

       X509_NAME_get_index_by_NID() and X509_NAME_get_index_by_OBJ() retrieve the next index matching nid or obj
       after lastpos. lastpos should initially be set to -1. If there are no more entries -1 is returned.  If
       nid is invalid (doesn't correspond to a valid OID) then -2 is returned.

       X509_NAME_entry_count() returns the total number of entries in name.

       X509_NAME_get_entry() retrieves the X509_NAME_ENTRY from name corresponding to index loc. Acceptable
       values for loc run from 0 to (X509_NAME_entry_count(name) - 1). The value returned is an internal pointer
       which must not be freed.

       X509_NAME_get_text_by_NID(), X509_NAME_get_text_by_OBJ() retrieve the "text" from the first entry in name
       which matches nid or obj, if no such entry exists -1 is returned. At most len bytes will be written and
       the text written to buf will be null terminated. The length of the output string written is returned
       excluding the terminating null. If buf is <NULL> then the amount of space needed in buf (excluding the
       final null) is returned.

       Process all entries:

        int i;
        X509_NAME_ENTRY *e;

        for (i = 0; i < X509_NAME_entry_count(nm); i++) {
            e = X509_NAME_get_entry(nm, i);
            /* Do something with e */
        }

       Process all commonName entries:

        int lastpos = -1;
        X509_NAME_ENTRY *e;

        for (;;) {
            lastpos = X509_NAME_get_index_by_NID(nm, NID_commonName, lastpos);
            if (lastpos == -1)
                break;
            e = X509_NAME_get_entry(nm, lastpos);
            /* Do something with e */
        }

       X509_NAME_get_index_by_NID, X509_NAME_get_index_by_OBJ, X509_NAME_get_entry, X509_NAME_entry_count,
       X509_NAME_get_text_by_NID, X509_NAME_get_text_by_OBJ - X509_NAME lookup and enumeration functions

X509_NAME_get_text_by_NID() and X509_NAME_get_text_by_OBJ() should be considered deprecated because they
       have various limitations which make them of minimal use in practice. They can only find the first
       matching entry and will copy the contents of the field verbatim: this can be highly confusing if the
       target is a multicharacter string type like a BMPString or a UTF8String.

       For a more general solution X509_NAME_get_index_by_NID() or X509_NAME_get_index_by_OBJ() should be used
       followed by X509_NAME_get_entry() on any matching indices and then the various X509_NAME_ENTRY utility
       functions on the result.

       The list of all relevant NID_* and OBJ_*codes can be found in the source code header files
       <openssl/obj_mac.h> and/or <openssl/objects.h>.

       Applications which could pass invalid NIDs to X509_NAME_get_index_by_NID() should check for the return
       value of -2. Alternatively the NID validity can be determined first by checking OBJ_nid2obj(nid) is not
       NULL.

X509_NAME_get_index_by_NID() and X509_NAME_get_index_by_OBJ() return the index of the next matching entry
       or -1 if not found.  X509_NAME_get_index_by_NID() can also return -2 if the supplied NID is invalid.

       X509_NAME_entry_count() returns the total number of entries, and 0 for failure.

       X509_NAME_get_entry() returns an X509_NAME pointer to the requested entry or NULL if the index is
       invalid.

ERR_get_error(3), d2i_X509_NAME(3)

        #include <openssl/x509.h>

        int X509_NAME_get_index_by_NID(const X509_NAME *name, int nid, int lastpos);
        int X509_NAME_get_index_by_OBJ(const X509_NAME *name,
                                       const ASN1_OBJECT *obj, int lastpos);

        int X509_NAME_entry_count(const X509_NAME *name);
        X509_NAME_ENTRY *X509_NAME_get_entry(const X509_NAME *name, int loc);

        int X509_NAME_get_text_by_NID(const X509_NAME *name, int nid,
                                      char *buf, int len);
        int X509_NAME_get_text_by_OBJ(const X509_NAME *name, const ASN1_OBJECT *obj,
                                      char *buf, int len);