fopen in c

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What is fopen in c?

fopen in c is used to open a file to do various tasks such as reading,writing.

It is defined in stdio.h header. It is a file handling function.

It returns a file pointer otherwise NULL if error occurs.

fopen in c works along with fclose function.

It takes two arguments. The file mode should be included to open a file.

Prototype of fopen

FILE *fopen(const char *fname, const char *mode);

Parameters of fopen

It takes a file pointer to point to a specific file and the mode like reading,writing is included to perform operation.

Return value of fopen

It returns a file pointer otherwise NULL if error occurs.

Example program for fopen in c

Example 1

#include<stdio.h>

int main()
{
   FILE *fpointer;
   fpointer=fopen("scholar.txt","w");
   fprintf(fpointer,"Hello,this is Scholarsoul");
   fclose(fpointer);
   return 0;
}
fopen in c example 1

Code explanation

The scholar.txt file is being opened with the help of a built-in function called fopen to perform tasks like writing the text into a file.


Example 2

#include<stdio.h>
int main()
{
  FILE *fpointer;
  int i;
  fpointer=fopen("scholar.txt","w");
  for(i=1;i<=3;i++)
     fprintf(fpointer,"%d\t",i);
  fclose(fpointer);
  return 0;
}
fopen in c example 2

Code explanation

The scholar.txt file is being opened with the help of a built-in function called fopen to perform tasks like writing some integer values into a file.

fopen() Man page


File opening modes in c programming

Now lets check various modes to open a file in c programming language.

ModeDescription
rOpen file for reading.
wOpen file for writing.
rbOpen file for reading in binary.
wbOpen file for writing in binary.
aOpen file for appending data.
abOpen file for appending data in binary.
r+Open file for reading and writing.
w+Open file for reading and writing.
rb+Open file for reading and writing in binary mode.
wb+Open file for reading and writing in binary mode.
a+Open file for reading and appending.
ab+Open file for reading and appending in binary mode.

Description

r: Stands for reading. We can open a file for reading purposes. We cannot perform a write operation if it is opened in reading mode.

w: Stands for write. By using this we can open a file for writing some data.

rb: Stands for read binary. We can open a file to read in binary mode.

wb: Stands for write binary. We can open a file to write in binary mode.

a: Stands for append. we can open a file for writing at its end.

ab: Stands for append binary. we can write data in append in binary mode.

r+: Open a file to read and write.

w+: Open a file to read and write.

rb+: Open a file to read and write in binary mode.

wb+: Open a file to read and write in binary mode.

a+: Open a file to read and append.

ab+: Open a file to read and append in binary mode.


Difference between fopen and fclose in c

fopen in c used to open a file to perform a task like reading/writing. fclose in c is used to close a file that is opened to perform a task.

fopen in c returns a file pointer otherwise NULL on error. fclose in c returns zero after successful operation otherwise EOF is returned as an error.

fopen works on a file in reading/writing mode. fclose only closes the file which was opened in reading/writing mode.

fopen uses the buffer. fclose flushes the buffer.

Prototypes are as follows

FILE *fopen(const char *fname,const char *mode);

int fclose(FILE *fp);
fopen in cfclose in c
Opens a file in read/write mode.Closes the file.
FILE *fopen(const char *fnmae,const char *mode);int fclose(FILE *fp);
Returns a file pointer otherwise NULL on error.Returns zero after successfull operation otherwise EOF is returned as error.
Uses the buffer.Flushes the buffer.

Difference between fopen and ftell in c

ftell in c is used to get the total size of a file. fopen in c used to open a file to perform a task like reading/writing.

ftell returns the current value of a file pointer. fopen in c returns a file pointer otherwise NULL on error.

ftell function works on open file. fopen opens a specific file.

ftell takes only one argument. fopen takes two arguments.

Prototypes are as follows

long int ftell(FILE *stm);

FILE *fopen(const char *fname,const char *mode);
ftell in cfopen in c
Used to get the total size of a file.Opens a file in read/write mode.
long int ftell(FILE *stm);FILE *fopen(const char *fnmae,const char *mode);
Returns the current value of a file pointer.Returns a file pointer otherwise NULL on error.
Works on open file.Opens a file.

Difference between fwrite and fopen in c.

fwrite writes data from the array pointed to a file as size_t object. fopen in c used to open a file to perform a task like reading/writing.

fwrite returns the total number of elements returned. fopen in c returns a file pointer otherwise NULL on error.

fwrite takes four arguments. fopen takes two arguments.

In fwrite function pointer points to an array of elements. In fopen function pointer points to a file.

Prototypes are as follows

size_t fwrite(const void *pt,size_t size,size_t nm,FILE *strm);

FILE *fopen(const char *fname,const char *mode);
fwrite in cfopen in c
Writes data from the array pointed to a file as size_t object.Used to open a file to perform a task like reading/writing.
Returns the total number of elements returned.Returns a file pointer otherwise NULL on error.
Takes four arguments.Takes two arguments.
size_t fwrite(const void *pt,size_t size,size_t nm,FILE *strm);FILE *fopen(const char *fname,const char *mode);

Difference between fseek and fopen in c

The fseek in c is used to change the file pointer for the specified stream. fopen in c used to open a file to perform a task like reading/writing.

fseek returns zero if successful operation otherwise it returns a non-zero value. fopen in c returns a file pointer otherwise NULL on error.

fseek seeks in an open file. fopen function opens a file.

in fseek pointer moves according to a value in whence parameter. fopen opens a pointed file.

Prototypes are as follows

int fseek(FILE *strm,long int offst,int whnce);

FILE *fopen(const char *fname,const char *mode);
fseek in cfopen in c
Used to change the file pointer for the specified stream.Used to open a file to perform a task like reading/writing.
Returns zero if successful operation otherwise it returns a non-zero value.Returns a file pointer otherwise NULL on error.
Seeks in an open file.Opens a file.
int fseek(FILE *strm,long int offst,int whnce);FILE *fopen(const char *fname,const char *mode);

Difference between fopen and fscanf in c

fscanf in c used to read formatted data from a file. fopen in c used to open a file to perform a task like reading/writing.

fscanf returns the number of fields converted and assigned. If an error occurs it returns EOF. fopen in c returns a file pointer otherwise NULL on error.

fscanf takes many arguments. fopen takes two arguments.

fopen takes mode as an argument. fscanf doesn’t take mode as an argument but it works on a file in whichever mode it is opened.

Prototypes are as follows

int fscanf(FILE *strm, const char *frmt,...);

FILE *fopen(const char *fname,const char *mode);
fscanf in cfopen in c
Used to read formatted data from a file.Used to open a file to perform a task like reading/writing.
Returns the number of fields converted and assigned.Returns a file pointer otherwise NULL on error.
int fscanf(FILE *strm, const char *frmt,...);FILE *fopen(const char *fname,const char *mode);
Takes many argumentsTakes only two arguments.

Difference between fopen and fprintf in c

fprintf function in c is used to format the output to a file instead of stdout console. fopen in c used to open a file to perform a task like reading/writing.

fprintf returns the number of characters written. if any error occurs it returns a negative value(-1). fopen in c returns a file pointer otherwise NULL on error.

fprintf takes many arguments. fopen takes two arguments.

fprintf works in a writing mode. fopen opens a file in read/write mode.

Prototypes are as follows

int fprintf(FILE *file_pointer, const  char *format_string,.......);

FILE *fopen(const char *fname,const char *mode);
fprintf in cfopen in c
It sends formatted data to a specified file.Used to open a file to perform a task like reading/writing.
Returns the number of characters written.if any error occurs it returns negative value(-1).Returns a file pointer otherwise NULL on error.
int fprintf(FILE *file_pointer, const char *format_string,.......);FILE *fopen(const char *fname,const char *mode);
Takes many arguments.Takes two arguments.

People also ask for

Which type of file cant be opened using fopen?

The files like .bin,.c cannot be opened using fopen. Other files like .txt file can be opened using fopen function.

What is the function of w+ mode in fopen?

It opens a file both in reading and writing mode. if in case of the file doesn’t exist it opens a new file.

What are BMP files?

BMP files are used to store bitmap image files. fopen and fclose functions are not allowed in BMP.

What are all the errors encountered if fopen fails?

Following are the errors if fopen fails.
1.EACCES
2.EINTR
3.EISDIR
4.ELOOP
5.EMFILE
6.ENFILE
7.ENOENT
8.ENOSPC
9.ENXIO
10.EROFS

What does fopen stands for?

It stands for file open. It opens a file stream.

What type does Fopen return?

Fopen returns pointer to FILE. If fails then returns null.

What does Fopen return if fails?

If fopen function fails then it returns null pointer.

What is fopen function?

fopen function in c programming language is used to open a file stream to perform read or write operation.

How do you use fopen?

we can use fopen by including stdio header file. Then calling fopen function by passing arguments file name and open mode.

What is fopen and fclose in C?

Fopen opens a file to perform reading and writing. Fclose releases all resources created bt fopen.