File is a structure defined in ‘stdio.h’ to handle file operations. Various operations like opening the file reading/writing in a file and closing the file can be done. The above operations can be done as shown below:
To Open a File:
- The syntax for opening the file is: File* fopen(char* name, char* mode);
- Opens the file ‘name’ and returns the FILE pointer.
- Values for ‘mode’ are ‘r’,’w’and ‘a’.
- fopen returns NULL if its unable to open file.
- If file does not exist, fopen will create file, if mode is ‘w’ or ‘a’.
Read/ Write to a File:
The syntax for reading or writing a character is shown below:
- Read a single character – int getc(FILE* fp);
- Write a single character – int putc(intc, FILE* fp);
Close a File – int fclose(FILE* fp);
Example – Opening a File:
#include<stdio.h>
int main()
{
FILE* fp;
char ch;
fp-fopen(“test.txt”, “r”);
do
{
ch=getc(fp);
printf(“%c”,ch);
}
while(ch !=EOF);
fclose(fp);
printf(“
”);
system(“PAUSE”);
return 0;
}Below is the file ‘test.txt’.
On compiling and running the program, the following output is obtained.
Program – When Trying To Open a File That Does Not Exist:
In case there is no file by name ‘test1’, the program returns the value NULL. In such cases, it needs to return the message “Unable to open the file.”
#include<stdio.h>
int main()
{
FILE* fp;
char ch;
fp-fopen(“test1.txt”, “r”);
if (fp == NULL)
{
printf(“Unable to open file
”);
system(“PAUSE”);
Return 0;
}
do
{
ch=getc(fp);
printf(“%c”,ch);
}
while(ch !=EOF);
fclose(fp);
printf(“
”);
system(“PAUSE”);
return 0;
}On compiling and running, the output as shown below:
Putting a Character in a File:
Example 1:
#include<stdio.h>
int main()
{
FILE* fp;
char ch;
fp-fopen(“test1.txt”, “r”);
if (fp == NULL)
{
printf(“Unable to open file
”);
system(“PAUSE”);
Return 0;
}
do
{
ch=getc(fp);
putc(ch,stdout);
}
while(ch !=EOF);
fclose(fp);
printf(“
”);
system(“PAUSE”);
return 0;
}The output is as shown below;
Example 2:
#include<stdio.h>
int main()
{
FILE* fp1,*fp2;
char ch;
fp1=fopen(“test1.txt”, “r”);
if (fp1 == NULL)
{
printf(“Unable to open file
”);
system(“PAUSE”);
Return 0;
}
fp2=fopen(“dest1.txt”, “w”);
if (fp2 == NULL)
{
printf(“Unable to open file
”);
system(“PAUSE”);
Return 0;
}
while((ch =getc(fp1)) != EOF)
{
putc(ch,fp2);
}
fclose(fp1);
printf(“
”);
system(“PAUSE”);
return 0;
}On running and compiling the program, a file with the name ‘dest1’ will be created with the content present in the file ‘test1’, in the folder.
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