C Pointer Programming Path---sixth notes

Pointers to file types
In C language files you read and write generally use the library functions of the system to read and write data
Pointer to the type of the file
Structure of the file
#include <iostream>
#include <cstdio>
using namespace Std;
typedef struct
{
Short level; The extent to which the buffer is full or empty
unsigned flags;File Status Flag
Char FD; File descriptor
unsigned hold;If no buffer does not read characters
Short basize; Size of the buffer
unsigned char *buffer;The location of the data buffer
unsigned char *curp;Pointer to the current point
unsigned istemp;Temporary files
Short token; Check for validity
}file;




Pointer to file
FILE *FP;


For example, the following example
Enter a character and display it in the screen
#include <stdio.h>
int main ()
{
char ch = getchar ();
Putchar ();
return 0;
}


The scanf () function prototype is
int scanf (char const *format ...);
//
Putchar () function
Prototype is
int Putchar (int character)
Example
#include <stdio.h>
int main ()
{
char ch = ' a ';
Puchar (CH); Output character A
Putchar (' \ n ');
Putchar (' abc ');Only one character is output
Putchar (' \101 ');Output character ' A '
Putchar (' \015 ');Output Enter, no wrapping, moves the cursor's current position to the beginning of the line
Putchar (' \ ');Output single quote character
return 0;
}




File processing field
function =====//function
Turn on or off fopen (), fclose ();
Read-write characters Fgetc (), FPUTC ();
Read and Write strings Fgets (), fputs ();
Read and write by data block Fread (), fwrite ()
Formatted read-write fscanf (), fprintf ()
File location Fseek (), Rewind (), Ftell ()
Determine if the file is closed Feof ();
//
Application Examples:
#include <iostream>
#include <cstdio>
using namespace Std;
int main (int argc, char *argv[])
{
Determine the number of parameters
if (argc! = 3)
{
printf ("The number of arguments not correct!\n");
Exit (1);
}


FILE *FPR, *FPW;
Open source file
if ((FPR = fopen (argv[1], ' r ')) = = = NULL)
{
printf ("Open source file error!");
Exit (1);
}


Open the destination file
if ((FPW = fopen (argv[2], ' w ')) = = NULL)
{

printf ("Open destination file error!");
Exit (1);
}


Char ch;
Copy source file to target file, read and write one character at a time
while ((ch = fget (FPR))! = EOF)
{
FPUTC (CH, FPW);
}
Close source file, target file
Fclose (FPR);
Fclose (FPW);
return 0;

}

Merges two integer files that have been sorted in ascending order to become a file sorted by incremental file
#include <iostream>
#include <cstdio>
using namespace Std;


int main ()
{
FILE *FP1;
FILE *FP2;
FILE *FP3;
int T1, T2;
if (AGRC! = 4)
{
printf ("The number of arguments not correct!\n");
Exit (1);
}




if ((FP1 = fopen (Argv[1], "r")) = = = NULL)
{
printf ("Open source File1 error\n");
Exit (1);
}


if ((FP2 = fopen (Argv[2], "r")) = = = NULL)
{
printf ("Open source File2 error\n");
Exit (1);
}


if ((FP3 = fopen (Argv[3], "r")) = = = NULL)
{
printf ("Open source File3 error\n");
Exit (1);
}


Fread (&t1, sizeof (int), 1, FP1);
Fread (&t2, sizeof (int), 2, FP2);

while (! feof (FP1) &&!feof (FP2))
{
if (T1 < T2)
{
Fwrite (&t1.sizeof (int), 1, FP3);
Fread (&t1, sizeof (int), 1, FP);
}
Else
{
Fwriter (&t2, sizeof (int), 1, FP3);
Fwriter (&t2, sizeof (int), 1, FP2);
}
}


while (! Feof (FP1))
{
Fwrite (&t1.sizeof (int), 1, FP3);
Fwrite (&t1,sizeof (int), 1, FP1);
}


while (!feof (FP2))
{
Fwrite (&t2, sizeof (int), 1, FP3);
Fwrite (&t2, sizeof (int), 1, FP2);
}
Fclose (FP1);
Fclose (FP2);
Fclose (FP3);
return 0;
}

C Pointer Programming Path---sixth notes