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5.4.39 mysql_hex_string()

unsigned long
mysql_hex_string(char *to,
                 const char *from,
                 unsigned long length)


This function creates a legal SQL string for use in an SQL statement. See String Literals.

The string in the from argument is encoded in hexadecimal format, with each character encoded as two hexadecimal digits. The result is placed in the to argument, followed by a terminating null byte.

The string pointed to by from must be length bytes long. You must allocate the to buffer to be at least length*2+1 bytes long. When mysql_hex_string() returns, the contents of to is a null-terminated string. The return value is the length of the encoded string, not including the terminating null byte.

The return value can be placed into an SQL statement using either X'value' or 0xvalue format. However, the return value does not include the X'...' or 0x. The caller must supply whichever of those is desired.


char query[1000],*end;

end = strmov(query,"INSERT INTO test_table values(");
end = strmov(end,"X'");
end += mysql_hex_string(end,"What is this",12);
end = strmov(end,"',X'");
end += mysql_hex_string(end,"binary data: \0\r\n",16);
end = strmov(end,"')");

if (mysql_real_query(&mysql,query,(unsigned int) (end - query)))
   fprintf(stderr, "Failed to insert row, Error: %s\n",

The strmov() function used in the example is included in the libmysqlclient library and works like strcpy() but returns a pointer to the terminating null of the first parameter.

Return Values

The length of the encoded string that is placed into to, not including the terminating null character.