What's wrong with my coding?

**EeeK** · 10-06-2003

If I entered "run.exe x.txt" in the following code, y does the if statement is always true?

Code:

int main(int argc, char *argv[])
{
 if(argv[1]!="x.txt")
 {
  printf("\nPlease enter run x.txt!!!\n");
  exit(1);
 }

In the following code, wat's wrong that causes it to loop infinitely when I entered a character instead of a integer?

Code:

int choice;

 while(choice!=2)
 {
  printf("\n1?");
  printf("\n2?");

  printf("\n\nChoice: ");
  scanf("%d", &choice);

  switch(choice)
  {
   case 1: 1(); break;
   case 2: break;
   default: printf("\nPlease enter 1 or 2 only!!!\n"); break;
  }
 }

Pls enlighten a newbie, thx a million....

**gunder** · 10-06-2003

I'm not sure about #1, I'm kinda new myself. #2 is answered in the faq though, right here

**EeeK** · 10-06-2003

Code:

while (cout << "Enter a number: " && !(cin >> input))
  {
    cout << "\nInvalid input" <<endl;
    cin.clear();
    cin.ignore(std::numeric_limits < int >::max(), '\n');
  }
  
  cout <<"You entered " <<input;

Went to the FAQ and it's in C++, what is the equivalent functions in C for clear() and ignore(std::numeric_limits <int>::max())?

Is it fflush(stdin) for clear()?

**Dave_Sinkula** · 10-06-2003

>If I entered "run.exe x.txt" in the following code, y does the if statement is always true?

>if(argv[1]!="x.txt")

Because this does not do a string comparison. Use strcmp.

Code:

if(strcmp(argv[1],"x.txt")!=0)

>Is it fflush(stdin) for clear()?

No. Try this.

**EeeK** · 10-06-2003

Y does I get a passing arg 2 of 'fputs' from incompatible pointer type error at the fputs() line?

Code:

define FILENAME "x.txt"
.
.
.
fp = fopen(FILENAME, "a");
 if(fp==(FILE*) NULL)
 {
  printf("\nError opening %s!!!\n", FILENAME);
  exit(1);
 }
 fputs("TEST", FILENAME);
 fclose(fp);

**cc0d3r** · 10-06-2003

fputs() expects a FILE * as its second argument, so use fputs("TEST", fp) instead.

**EeeK** · 10-06-2003

Yup, found out abt that but u post b4 I want to delete the post. Nonetheless thx for the reply.

**EeeK** · 10-06-2003

What is the difference btn these 3:

Code:

char* text;
char *text;
char text[99];

The second is a char pointer and third is an array, so what is first? Can I use all of them for fgets() or only the third can be use on fgets() as fgets(text, 99, stdin)?

**cc0d3r** · 10-06-2003

First and second are examples of the different styles of using '*' operator, but are otherwise equivalent.

**EeeK** · 10-06-2003

So they are basically the same. So can I use the first and the second for fgets()? Because the middle arguments of fgets() is the buffer size. which is not define if I'm using the first and second.

If not what are the ways in accepting a string input?

Code:

...
printf("Enter your name:");
...

**Dave_Sinkula** · 10-06-2003

>So they are basically the same.

I'd better point here again.

>So can I use the first and the second for fgets()?

Not unless you allocate memory to where these pointers point.

Code:

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
   char automatic[10];
   char *dynamic;
   size_t size = 42;

   puts("Enter 'automatic' string:");
   fflush(stdout);
   if(fgets(automatic, sizeof automatic, stdin) != NULL)
   {
      printf("automatic: %s\n", automatic);
   }

   dynamic = malloc(size);
   if(dynamic != NULL)
   {
      puts("Enter 'dynamic' string:");
      fflush(stdout);
      if(fgets(dynamic, size, stdin) != NULL)
      {
         printf("dynamic: %s\n", dynamic);
      }
      free(dynamic);
   }

   return 0;
}

/* my output
Enter 'automatic' string:
All work and no play makes Jack a dull boy.
automatic: All work 
Enter 'dynamic' string:
dynamic: and no play makes Jack a dull boy.
*/

**EeeK** · 10-07-2003

Ok what is the difference btn

Code:

char *x;
x = (char*)malloc(sizeof(char)*9);

and

Code:

char x[9];

**Moni** · 10-07-2003

As far as I know

using malloc dynamically allocate memory...while running
and arrays set aside fixed sized memory before using it....

**DrZoidberg** · 10-07-2003

A C compiler completely ignores most whitespaces and linebreaks. i.e. it doesn't make any difference if you write

Code:

char* text;

or

char *text;

or

char*text;

or

char

*

   text

;

**DrZoidberg** · 10-07-2003

Originally posted by Moni
As far as I know

using malloc dynamically allocate memory...while running
and arrays set aside fixed sized memory before using it....

Arrays also allocate memory while running. And malloc is beeing used to set aside a fixed size memory before using it.

The difference is that for arrays this allocation is done automatically with malloc you do it manually. Also the size of an array can not be changed. You can not assign another piece of memory to an array variable as you can do with a pointer variable.

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