C programming input and output functions

C file I/O is second part of C input and output functions in C language. In this chapter you will understand C programming file i/o examples. In addition, you can find file i/o in C using system calls. However, to know more C language file I/O, you can continue reading.  Finally, you will know about C binary file I/O as well.

What is file I/O in C tutorials?

In this chapter, you will go in detail about C programming file I/O functions. Plus, you will know process for creating or opening or closing text. Even binary files follow these steps. As this will help them with data storage.

What is file in C language?

File indicates sequence of bytes in C language. Moreover, these can be either binary or text file. It is also easy to handle files in storage devices. It is so because programming language has options to access functions. These functions can be high level or low level (OS level) calls.

Opening files in C programming language

Here you will learn opening multiple files in C language. In addition opening binary files in C is easy. fopen() function is useful to create new file. Moreover, you can open existing file as well. This function initializes object of type FILE. And this will have information on controlling stream.

Prototype of fopen() function is –

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

In prototype, filename is string literal. This will name files. While access mode may have any one of the following values –

Closing files in C programming

You may even close files. But for this you must use fclose( ) function. And below you can find prototype of function

int fclose(  FILE  *fp  );

If successful, then fclose(-) function returns zero. However, it can be EOF also. This happens when there is error in closing files in C language. In addition, this function will remove data that is in buffer to file.

It will then close file and even release memory used for file. This EOF is constant. In addition, definition of it is in header file stdio.h. C standard library gives functions. These help you to read and write character by character. This list includes file or fixed length string.

Writing files in C programming language

Function to write characters to stream is –

int fputc( int c, FILE *fp );

fputc() function will write character value of argument c. This is for output stream which fp refers. Moreover, it will return written character on success. However, if there is error then it will be EOF.

You can write null terminated string to stream in following manner –

int fputs( const char *s, FILE *fp );

Besides, you must remember that fputs() function will write string s to output stream. Moreover, fp refers it. But it will return non negative value on success. While for errors, EOF returns.

To write C strings in file, you will use following function –

int fprintf(FILE *fp,const char *format, …)

Example program

Reading a file in C programming language online tutorial

Function for reading single character from file –

int fgetc( FILE * fp );

Function fgetc() reads character from input file. In addition, fp refers it. Return value is character read. However, for errors, EOF returns.

Function to read string from stream

char  *fgets(  char  *buf ,  int  n,  FILE  *fp  );

Another aspect is that fgets() function will read till n-1 characters. Moreover., this is from input stream. Finally fp refers it. It will copy read string in buffer. Therefore, we add null character. As this will terminate string in C.

Read following example to understand it in a better way. However, remember one more point. You may use following function to read string –

int fscanf(FILE *fp, const char *format, …)

Example program

Binary I/O functions in C programming language

In C programming language, you will use binary input and output functions. In addition, you will use these functions to either write or read block of memories. Apart from this, memories here are structures(in C) and arrays(in C).In addition, you may check C functions.

Binary I/O functions in C language

fread(void *ptr, size_t size_of_elements, size_t number_of_elements, FILE *a_file); size_t fwrite(const void *ptr, size_t size_of_elements, size_t number_of_elements, FILE *a_file);