C Open File
Description
You open a file by calling function fopen(), which returns the file pointer for a file.
Syntax
The function fopen() is defined in <stdio.h>, and
it has this prototype:
FILE *fopen(char *name, char *mode);Parameter
The first argument is the file name in string. The second argument is a character string called the file mode that specifies what you want to do with the file.
Mode
The following table lists these three file modes.
| Mode | Description |
|---|---|
| "w" | Open a text file for write operations. If the file exists, its current contents are discarded. |
| "a" | Open a text file for append operations. All writes are to the end of the file. |
| "r" | Open a text file for read operations. |
Example 1
#include<stdio.h>
/*w w w. j a va2s .c om*/
void main(){
FILE *fp;
fp = fopen("test.txt","a");
fprintf(fp,"%d %s %d\n",1,"java2s.com",2);
fclose(fp) ;
}
Example 2
#include "stdio.h"
/*from w w w. j a va 2 s .c om*/
int main() {
FILE *fp;
int letter;
if( ( fp = fopen( "my.txt", "r")) == NULL) {
puts("Cannot oepn the file");
exit( 0 );
}
while( ( letter = fgetc( fp ) ) != EOF)
printf("%c",letter);
fclose(fp);
}