By default, SQL Plus treats &#39;&amp;&#39; as a special character that begins a substitution string.  This can cause problems when running scripts that happen to include &#39;&amp;&#39; for other reasons:

    SQL&gt; insert into customers (customer_name) values (&#39;Marks &amp; Spencers Ltd&#39;);
    Enter value for spencers: 
    old   1: insert into customers (customer_name) values (&#39;Marks &amp; Spencers Ltd&#39;)
    new   1: insert into customers (customer_name) values (&#39;Marks  Ltd&#39;)
    
    1 row created.
    
    SQL&gt; select customer_name from customers;
    
    CUSTOMER_NAME
    ------------------------------
    Marks  Ltd

If you know your script includes (or may include) data containing &#39;&amp;&#39; characters, and you do not want the substitution behaviour as above, then use `set define off` to switch off the behaviour while running the script:

    SQL&gt; set define off
    SQL&gt; insert into customers (customer_name) values (&#39;Marks &amp; Spencers Ltd&#39;);
    
    1 row created.
    
    SQL&gt; select customer_name from customers;
    
    CUSTOMER_NAME
    ------------------------------
    Marks &amp; Spencers Ltd

You might want to add `set define on` at the end of the script to restore the default behaviour.

Here is the example:

    SQL&gt; set define off;
    SQL&gt; select * from dual where dummy=&#39;&amp;var&#39;;
    
    no rows selected
    
    SQL&gt; set define on
    SQL&gt; /
    Enter value for var: X
    old   1: select * from dual where dummy=&#39;&amp;var&#39;
    new   1: select * from dual where dummy=&#39;X&#39;
    
    D
    -
    X

With `set define off`, it took a row with `&amp;var` value, prompted a user to enter a value for it and replaced `&amp;var` with the entered value (in this case, `X`).


The answers to questions like this: https://stackoverflow.com/questions/400135/c-sharp-listt-or-ilistt always seem to agree that returning an interface is better than returning a concrete implementation of a collection. But I&#39;m struggling with this. Instantiating an interface is impossible, so if your method is returning an interface, it&#39;s actually still returning a specific implementation. I was experimenting a bit with this by writing 2 small methods:

    public static IList&lt;int&gt; ExposeArrayIList()
    {
        return new[] { 1, 2, 3 };
    }

    public static IList&lt;int&gt; ExposeListIList()
    {
        return new List&lt;int&gt; { 1, 2, 3 };
    }

And use them in my test program:

    static void Main(string[] args)
    {
        IList&lt;int&gt; arrayIList = ExposeArrayIList();
        IList&lt;int&gt; listIList = ExposeListIList();
        
        //Will give a runtime error
        arrayIList.Add(10);
        //Runs perfectly
        listIList.Add(10);
    }

In both cases when I try to add a new value, my compiler gives me no errors, but obviously the method which exposes my array as an `IList&lt;T&gt;` gives a runtime error when I try to add something to it. 
So people who don&#39;t know what&#39;s happening in my method, and have to add values to it, are forced to first copy my `IList` to a `List` to be able to add values without risking errors. Of course they can do a typecheck to see if they&#39;re dealing with a `List` or an `Array`, but if they don&#39;t do that, and they want to add items to the collection **they have no other choice to copy the `IList` to a `List`, even if it already is a `List`**. Should an array never be exposed as `IList`?

Another concern of mine is based upon the accepted answer of the [linked question][1] (emphasis mine):

&gt; If you are exposing your class through a library that others will use, **you generally want to expose it via interfaces rather than concrete implementations.** This will help if you decide to change the implementation of your class later to use a different concrete class. In that case the users of your library won&#39;t need to update their code since the interface doesn&#39;t change.

&gt;If you are just using it internally, you may not care so much, and using List&lt;T&gt; may be ok.

Imagine someone actually used my `IList&lt;T&gt;` they got from my `ExposeListIlist()` method just like that to add/remove values. Everything works fine. But now like the answer suggests, because returning an interface is more flexible I return an array instead of a List (no problem on my side!), then they&#39;re in for a treat...

TLDR: 

1) Exposing an interface causes unnecessary casts? Does that not matter?

2) Sometimes if users of the library don&#39;t use a cast, their code can break when you change your method, even though the method remains perfectly fine.

I am probably overthinking this, but I don&#39;t get the general consensus that returning an interface is to be preferred over returning an implementation.


  [1]: https://stackoverflow.com/a/400144/3410196

Is returning IList&lt;T&gt; worse than returning T[] or List&lt;T&gt;?

I have the following query.Could any one please suggest me a solution.

I&#39;m working on encryption and decryption of file for first time.

I have encrypted file through command prompt using the command:

    openssl enc -aes-256-cbc -in file.txt -out file.enc -k &quot;key value&quot; -iv &quot;iv value&quot;

I have to decrypt it programmatically. So I have written the program for it, but it is throwing the following error:

    ./exe_file enc_file_directory
    ...
    error: 06065064: digital envelope routines: EVP_DecryptFInal_ex: bad decrypt: evp_enc.c

----

The program below takes input as directory path and search for encrypted file &quot;.enc&quot; and try to decrypt it read into buffer.

Code:

	#include &lt;stdio.h&gt;
	#include &lt;string.h&gt;
	#include &lt;stdlib.h&gt;
	#include &lt;dirent.h&gt;
	#include &lt;sys/stat.h&gt;
	#include &lt;sys/types.h&gt;
	#include &lt;openssl/evp.h&gt;
	#include &lt;openssl/err.h&gt;
	#include &lt;openssl/conf.h&gt;
	#include &lt;libxml/globals.h&gt;

	void handleErrors(char *msg)
	{
	    {
        	ERR_print_errors_fp(stderr);
	        printf(&quot;%s&quot;, msg);
	        abort(); 
	    }
	}

	void freeMemory(char *mem)
	{
	    if (NULL != mem)
	    {
        	free(mem);
	        mem = NULL;
	    }
	}

	/* Function to decrypt the XML files */

	int decryptXML(unsigned char *indata, unsigned char *outdata, int fsize)
	{

	    int outlen1 = 0, outlen2 = 0;
    
	    unsigned char iv[] = &quot;b63e541bc9ece19a1339df4f8720dcc3&quot;;
	    unsigned char ckey[] = &quot;70bbc518c57acca2c2001694648c40ddaf19e3b4fe1376ad656de8887a0a5ec2&quot; ;
  
	    if (NULL == indata)
	    {
	        printf (&quot;input data is empty\n&quot;);
	        return 0;
	    }
    
	    if (0 &gt;= fsize)
	    {
	        printf (&quot;file size is zero\n&quot;);
        	return 0;
	    }

	    outdata = (char *) malloc (sizeof (char) * fsize * 2);

	    EVP_CIPHER_CTX ctx;
 
	    EVP_CIPHER_CTX_init(&amp;ctx);

	    if (! EVP_DecryptInit_ex (&amp;ctx, EVP_aes_256_cbc(), NULL, ckey, iv))
	    {
	        EVP_CIPHER_CTX_cleanup(&amp;ctx);
		handleErrors(&quot;DInit&quot;);
	    }

	    if (! EVP_DecryptUpdate (&amp;ctx, outdata, &amp;outlen1, indata, fsize))
	    {
        	EVP_CIPHER_CTX_cleanup(&amp;ctx);
	        handleErrors(&quot;DUpdate&quot;);
	    }

	    if (! EVP_DecryptFinal_ex (&amp;ctx, outdata + outlen1, &amp;outlen2))
	    {

	        EVP_CIPHER_CTX_cleanup(&amp;ctx);
        	handleErrors(&quot;DFinal&quot;);
	    }

	    EVP_CIPHER_CTX_cleanup(&amp;ctx);

	    return outlen1+outlen2;

	}

	int isDirectory(char *path)
	{
	    DIR *dir = NULL;
	    FILE *fin = NULL, *fout = NULL;
	    int enc_len = 0, dec_len = 0, fsize = 0, ksize = 0;
	    unsigned char *indata = NULL, *outdata = NULL;
	    char buff[BUFFER_SIZE], file_path[BUFFER_SIZE], cur_dir[BUFFER_SIZE];

	    struct dirent *in_dir;
	    struct stat s;

	    if (NULL == (dir = opendir(path)))
	    {
	        printf (&quot;ERROR: Failed to open the directory %s\n&quot;, path);
	        perror(&quot;cannot open.&quot;);
        	exit(1);
	    }

	    while (NULL != (in_dir = readdir(dir)))
	    {

	        if (!strcmp (in_dir-&gt;d_name, &quot;.&quot;) || !strcmp(in_dir-&gt;d_name, &quot;..&quot;))
        	    continue;

	        sprintf (buff, &quot;%s/%s&quot;, path, in_dir-&gt;d_name);
    
    	    if (-1 == stat(buff, &amp;s))
        	{
	            perror(&quot;stat&quot;);
        	    exit(1);
	        }
        
        	if (S_ISDIR(s.st_mode))
	        {
            
        	    isDirectory(buff);
	        }
        	else
        	{
	            strcpy(file_path, buff);
	
	            if (strstr(file_path, &quot;.enc&quot;))
        	    {
	            
        	        /* File to be decrypted */
                
                	fout = fopen(file_path,&quot;rb&quot;); 

	                fseek (fout, 0L, SEEK_END);
	                fsize = ftell(fout);
	                fseek (fout, 0L, SEEK_SET);

	                indata = (char*)malloc(fsize);

	                fread (indata, sizeof(char), fsize, fout);

	                if (NULL == fout)
        	        {
                	    perror(&quot;Cannot open enc file: &quot;);
	                    return 1;
        	        }
              

	                dec_len = decryptXML (indata, outdata, fsize);
        	        outdata[dec_len] = &#39;\0&#39;;
                	printf (&quot;%s\n&quot;, outdata);
	                fclose (fin);
        	        fclose (fout);

        	    }
	        }
	    }



	    closedir(dir);
	    freeMemory(outdata);
	    freeMemory(indata);

	    return 1; 
	}


	int main(int argc, char *argv[])
	{
	    int result;
    
	    if (argc != 2)
	    {
	        printf (&quot;Usage: &lt;executable&gt; path_of_the_files\n&quot;);
        	return -1;
	    }

	    ERR_load_crypto_strings();
	    OpenSSL_add_all_algorithms();
	    OPENSSL_config(NULL);

	    /* Checking for the directory existance */

	    result = isDirectory(argv[1]);

	    EVP_cleanup();
	    ERR_free_strings();

	    if (0 == result)
        	return 1;
	    else
 	       return 0;
	}

Thank you.

How to resolve the &quot;EVP_DecryptFInal_ex: bad decrypt&quot; during file decryption

I&#39;m watching a Script in Oracle and I see something I don&#39;t recognize
    
    REM INSERTING into database1.&quot;Users&quot;
     SET DEFINE OFF;
    Insert into database1.&quot;Users&quot; (&quot;id&quot;,&quot;right&quot;) values (&#39;1&#39;,&#39;R&#39;);

I&#39;m looking for documentation about &quot;set define off&quot; and it&#39;s literally writing &quot;disable the parsing of commands to replace substitution variable with their values&quot;

I don&#39;t really understand what they want to say.

Can anyone help me?

When or Why to use a &quot;SET DEFINE OFF&quot; in Oracle Database

I'm watching a Script in Oracle and I see something I don't recognize
<pre><code class="hljs language-sql">REM INSERTING into database1."Users"
 SET DEFINE OFF;
Insert into database1."Users" ("id","right") values ('1','R');
</code></pre>
I'm looking for documentation about "set define off" and it's literally writing "disable the parsing of commands to replace substitution variable with their values"
I don't really understand what they want to say.
Can anyone help me?

I created the table Test_Project2 in Oracle SQL Developer. After that I realized that the column proj_name is of a small size, so I decided to modify the column using the follwoing statement

	ALTER TABLE TEST_PROJECT2 MODIFY proj_name VARCHAR2(300);
	
but for some reason Oracle SQL Developer underscores the semi-colon with red and I do not what is mistake and how to correct it

**Test_Project2**:

	CREATE TABLE Test_Project2 (
	proj_id number(30),
	proj_name VARCHAR2 (30),
	proj_desc VARCHAR2(300)
	);

how to modify the size of a column

I&#39;m facing the problem about my database in Oracle, When I opened my database, it appear a message with: &quot;ORA-28001: The password has expired&quot;

I have updated my account with somes:

    sqlplus /nolog
    SQL&gt; connect / as SYSDBA
    Connected.

    SQL&gt; SELECT username, account_status FROM dba_users WHERE ACCOUNT_STATUS LIKE &#39;%EXPIRED%&#39;;

    SQL&gt; ALTER USER system IDENTIFIED BY system;         
    User altered.

    SQL&gt; ALTER USER system ACCOUNT UNLOCK;
    User altered.

    SQL&gt; ALTER PROFILE DEFAULT LIMIT PASSWORD_LIFE_TIME UNLIMITED;
    Profile altered.

    SQL&gt; exit

I check and see that, my account: &#39;system&#39; has OPEN, but I open it on Oracle SQL Developer, it still have alert: 

    ORA-28001: The password has expired

I have refered very much links but it still same the problem, how to fix this?

ORA-28001: The password has expired

I downloaded Windows 64-bit with JDK 8 included of SQL Developer 18.1.

To run Oracle SQL Developed I just unzipped the file and run the sqldeveloper.exe contained in the folder.

Unfortunately, as you can see in the image the size of everything is extremely small and very difficult to see.[![enter image description here][1]][1]

This issue appears exclusively with this software.

How can I resolve it? 

  [1]: https://i.stack.imgur.com/g3Znw.png

Content Type	Original Author	Original Content on Stackoverflow
Question	Enrique Benito Casado	View Question on Stackoverflow
Solution 1 - Oracle	Tony Andrews	View Answer on Stackoverflow
Solution 2 - Oracle	Durga Viswanath Gadiraju	View Answer on Stackoverflow

When or Why to use a "SET DEFINE OFF" in Oracle Database

Oracle Problem Overview

Oracle Solutions

Solution 1 - Oracle

Solution 2 - Oracle

How to resolve the "EVP_DecryptFInal_ex: bad decrypt" during file decryption

Is returning IList<T> worse than returning T[] or List<T>?

Attributions