FILE I/O in C Language or File Handling in C Language:
File Type
|
|
Data File
|
Text File
|
Stored
Records in a Format
|
Stored
Text without any format
|
Structured
File
|
Un-Structured
File
|
Like
MS Access
|
Like
MS Word, Notepad File, etc.
|
=> We can create a
Text or Data File
using C programs and can perform many task (operations) on it.
=> We can perform operations
on files like Writing data, Adding and Modifying data, Deleting data, Accessing
Record/Text, etc.
=> We have to open a file
with a specific accessing mode like read, write or append.
File Opening Mode
|
|
Operation
|
Key
|
Write
|
“w”
|
Read
|
“r”
|
Append
|
“a”
|
FILE Pointer:- We have to require a platform to open a file
to perform an operation, called File Pointer.
FILE:- This is a constant and used to declare a File Pointer to handle
a file.
Syntax:
FILE
*file-pointer;
Example:
FILE
*FP;
fopen( ) :- This function is used to open a
file using a file-pointer with a specific opening mode. Required a header file
“stdio.h”.
Syntax:
file-pointer=fopen(“file-name” , “opening-mode”);
Example:
FP=fopen(“STUD.DAT”, “w”);
fclose( ) :- This function is used to close an opened file after completing the task. Required a
header file “stdio.h”.
Syntax:
fclose(file-pointer);
Example:
fclose(FP);
~~~~~~@~~~~~~
Write Process (Store Data): INPUT
scanf( ) fprintf( )
Keyboard =========> Memory ===========> File
Read Process (Access Data):
OUTPUT
fscanf( ) printf( )
File ===============>
Memory =============> Monitor
fprintf( ) :- This function is
used to store (write) data from memory to a file.
It requires a header file “stdio.h”.
Syntax:
fprintf(file-pointer,
“format specifier”, variable-name);
Ex:
int RN;
char NAME[12];
float PER;
fprintf(FP,“%d
%s %f”, RN, NAME, PER);
fscanf( ) :- This function is used to read
data from a file to memory. It requires a header file “stdio.h”.
Syntax:
fscanf(file-pointer,
“format specifier”, &variable-name);
Ex:
int RN;
char NAME[12];
float PER;
fscanf(FP,“%d
%s %f”, &RN, &NAME, &PER);
~~~~~~@~~~~~~
//
Store/write following information of 5 students
in a data file:
Roll Number, Name and Percentage. S_WRITE.C
#include<stdio.h>
#include<conio.h>
void
main( )
{
int RN, i ;
char NAME[10];
float PER;
FILE
*FP;
FP=fopen(“STUD.DAT” , “w”);
clrscr( );
if(FP==NULL)
{
printf(“File can not be
created”);
exit( );
}
printf(“Input following information of 5
students… \n”);
for(i=1; i<=5; i++)
{
printf(“Input Roll Number = “);
scanf(“%d”, &RN);
printf(“Input Name = “);
scanf(“%s”, &NAME);
printf(“Input Percentage = “);
scanf(“%f”, &PER);
fprintf(FP,
“%d %s %f\n”, RN, NAME, PER);
}
fclose(FP);
printf(“\n Student data file created
successfully”);
}
~~~~~~@~~~~~~
//
Reading student records from a data file:
Roll Number, Name & Percentage. S_READ1.C
#include<stdio.h>
#include<conio.h>
void
main( )
{
int RN, i ;
char NAME[10];
float PER;
FILE
*FP;
FP=fopen(“STUD.DAT” , “r”);
clrscr( );
if(FP==NULL)
{
printf(“File can not be Opened”);
exit( );
}
printf(“ROLL NO. NAME PERCENTAGE \n”);
for(i=1; i<=5; i++)
{
fscanf(FP,
“%d %s %f\n”, &RN, &NAME, &PER);
printf(“%d %s %f\n”, RN, NAME,
PER);
}
fclose(FP);
}
~~~~~~@~~~~~~
Error Handling in FILE I/O:
NULL :- This constant is
used to check possibility of making/opening a file.
if(FP==NULL)
{
printf(“File can not be created or
opened”);
}
EOF :- This constant is
used to check record pointer for approaching end of the file. (Text File)
feof( ) :- This function is
used to check record pointer for approaching end of the file. (Data File)
while(feof(FP)==0)
{
Accessing/reading Records
}
OR
while(feof(FP))
{
Accessing/reading Records
}
~~~~~~@~~~~~~
fputc( ) :- This function is
used to write (store) a character to the text
file. It requires a header file “conio.h”.
Syntax:
fputc(Character-Variable , File-Pointer);
Ex:
char CH;
fputc(CH, FP);
13
=> This is an ASCII code of ENTER Key.
27
=> This is an ASCII code of ESC / ESCAPE Key.
//
Write a C program to create a text file to store some text. (press ESC key to exit from file) T_WRITE.C
#include<stdio.h>
#include<conio.h>
void
main()
{
char CH;
FILE *FP;
clrscr();
FP=fopen("mydoc .txt","w");
if(FP==NULL)
{
printf("Text file cannot be
created");
exit();
}
while((CH=getche())!=27)
{
if(CH==13)
{
fputc('\n' , FP);
printf("\n");
}
else
{
fputc(CH, FP);
}
}
fclose(FP);
printf("\n A text file is created");
}
~~~~~~@~~~~~~
fgetc( ) :- This function is
used to READ a character from a text file. It
requires a header file “conio.h”.
Syntax:
char-Variable = fgetc(File-Pointer);
Ex:
char CH;
CH = fgetc(FP);
//
Write a C program to read text from previously created text file. T_READ.C
#include<stdio.h>
#include<conio.h>
void
main()
{
char CH;
FILE *FP;
clrscr();
FP=fopen("mydoc .txt","r");
if(FP==NULL)
{
printf("File cannot be
opened");
exit();
}
while((CH=fgetc(FP))!=EOF)
{
printf("%c",CH);
}
fclose(FP);
}
~~~~~~@~~~~~~
//
Write a C program to copy text from one file to another file. F_COPY.C
#include<stdio.h>
#include<conio.h>
void
main()
{
char CH;
FILE *SFP,*DFP;
clrscr();
SFP = fopen("mydoc.txt","r");
if(SFP==NULL)
{
printf("Source file can not
be opened");
exit();
}
DFP =
fopen("yourdoc.txt","w");
if(DFP==NULL)
{
printf("Destination file
can not be created");
fclose(SFP);
exit();
}
while((CH=fgetc(SFP))!=EOF) //Copy Process
{
fputc(CH, DFP);
}
fclose(SFP);
fclose(DFP);
printf("\n1 file(s) copied");
}
~~~~~~@~~~~~~
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