Converting string to char array

**frankchester** · 11-30-2010

Hi, I have another problem

I've written a program which reads in a text file into a string.

Now, I want to convert that entire string so each char is held seperately in an array.

Basically I'm not sure how to pluck each character out of the string and store it seperately?

Code:

/*Program to read in text file and store data in a string*/

#include<stdio.h>

void main()
{
	/*declare and initialise variable*/
	char message[400];
	int i=0;

	FILE *file_in;
	file_in=fopen("text.txt", "r");

	/*stores and prints the data from the string*/
	fgets (message , 400 , file_in);
    puts (message);

}

**cas** · 11-30-2010

But your string already is an array of char.

If you want to access each char, you just have to look at message[0], message[1], up until you find a zero (which marks the end of a string). If you want to copy a string, you can use strcpy() (make sure the target buffer is large enough).

What is your ultimate goal?

**frankchester** · 11-30-2010

Originally Posted by cas

But your string already is an array of char.

If you want to access each char, you just have to look at message[0], message[1], up until you find a zero (which marks the end of a string). If you want to copy a string, you can use strcpy() (make sure the target buffer is large enough).

What is your ultimate goal?

The next step of this program is to encrypt it using a caesar cipher, thus I figured I'd need to have each char as separated as possible so that I cna encrypt each separately. Will I be able to encrypt just by selecting which one by its number?

**~~CommonTater~~** · 11-30-2010

Originally Posted by frankchester

The next step of this program is to encrypt it using a caesar cipher, thus I figured I'd need to have each char as separated as possible so that I cna encrypt each separately. Will I be able to encrypt just by selecting which one by its number?

That's going to depend how you write your code... but Yes that is one way of doing it.

By way of agreeing with the others, C doesn't know strings. In C a string is simply an array of char that some library functions treat as a string.

You have declared char message[400]; that sure looks like an array to me

**quzah** · 11-30-2010

Originally Posted by CommonTater

By way of agreeing with the others, C doesn't know strings. In C a string is simply an array of char that some library functions treat as a string.

You and everyone you are agreeing with are wrong. The standard implicitly defines what a string is.

"A string is a contiguous sequence of characters terminated by and including the first null character. The term multibyte string is sometimes used instead to emphasize special processing given to multibyte characters contained in the string or to avoid confusion with a wide string. A pointer to a string is a pointer to its initial (lowest addressed) character. The length of a string is the number of characters preceeding the null characters and the value of a string is the sequence of the values of the contained characters, in order."

Quzah.

**Jesius** · 11-30-2010

You have stored the text in the array, you can use it directly.

**~~CommonTater~~** · 11-30-2010

Originally Posted by quzah

You and everyone you are agreeing with are wrong. The standard implicitly defines what a string is.

"A string is a contiguous sequence of characters terminated by and including the first null character.

And how is that stored... in an array.

**whiteflags** · 12-01-2010

So, by definition, C knows strings.

**~~CommonTater~~** · 12-01-2010

Originally Posted by whiteflags

So, by definition, C knows strings.

No, Pascal knows strings... lots of other languages know strings... they have data types for just the purpose and can manipulate them natively.

Code:

// pascal version
Program Hello;

var 
string s;
string c;

begin
   s := "hello";
   c := s;
   s := " world";
  
  write ( c );     // output = hello world
  write ( s );  

end.


// C version
#include stdio.h

char s[10];
char c[10];

int main(void)
  { strcpy(s,"hello");
     c = s;
     strcpy(s,"world");

     puts( c );    // output  = world world
     puts( s );    // and a memory leak
  }

C has no native string awareness.

**whiteflags** · 12-01-2010

So "hello" and "world" are not strings even though they clearly fit the definition of what a string is, and facilities are provided to manipulate them? Pascal may be arguably better at manipulating text, but that's all a matter of opinion.

**Bayint Naung** · 12-01-2010

C has no native string awareness.

Really?
as whiteflags has pointed out."hello" is a string. (C string). Compiler does some work behind the scene.
Btw, How come there's a memory leak when you are using local variable?
Edit: not to mention that you can't assign array. c = s

**laserlight** · 12-01-2010

Originally Posted by CommonTater

In C a string is simply an array of char that some library functions treat as a string.

This is false. In C a string is not simply an array of char. The part that is missing is the fact that the contiguous sequence of characters has to be terminated by a null character in order to be considered a string.

Frankly, I think that cas' point is pretty much correct: frankchester's string already is an array of char. It might not be terribly accurate if we want to be really pedantic (since string length and array size are two different things), but it does not matter since it gets the idea across to frankchester.

Originally Posted by CommonTater

No, Pascal knows strings... lots of other languages know strings... they have data types for just the purpose and can manipulate them natively.

Show me a programming language that can manipulate strings easily and I will show you a natural language that can talk

In other words, there is no programming language that knows strings, because programming languages don't know, no more than natural languages talk or write. What you probably meant to say is that there is no primitive string data type in C, with strings being more of a standard convention with some support for string literals and with some library functions operating on the standard notion of a string.

**Bayint Naung** · 12-01-2010

@laserlight, I am in total agreement with your point.

**~~CommonTater~~** · 12-01-2010

I give up....

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