File Processing

FILE PROCESSING

SUB TOPICS :

• Files and Streams
• File Definition
• Open File
• Close File
• Input File
• Output File

Files and Streams

Streams Definition

•      To keep key in data from keyboard need to be saved at secondary storage device as a data file.

•      Stream is a sequence of character. All input and output data is a stream. C sees file as a stream.

•       When a C program run, there are three (3) standard streams activated:

1. Standard Input Stream

    Controlling input stream from keyboard

2. Standard Output Stream

    Controlling output stream to the monitor

3. Standard Error Stream

    Controlling the error messaging

•       Each stream associated with a file.

File Definition

•       File is a collection of record

•       Record is a collection of field

•       Field is a block of byte

•       Byte is collection of bit

   Open File

•      Opening a File using fopen():

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

•      fopen() defined at <stdio.h>

•      fopen() return a pointer to the start of a buffer area. Null will be returned if file unable to open.

    Mode                                Description

                “r”                                          opening a file to be read.

                “w”                                        creating a file to be written.

                “a”                                          opening a File for data append.

                “r+”                                        opening a File for read/write.

                “w+”                      creating file for read/write.

                “a+”                                       opening a File for read/append

                “rb”                                       opening a File (binary) to be read.

                “wb”                     creating a file (binary) for write operation.

   Close File

      int fclose (FILE *stream);

•      fclose() defined at <stdio.h>

•      fclose() will return 0 if successful, and EOF if error

•      EOF (End Of File) equals to  -1

•      fclose() will release the buffer area and immediately send the remaining data to file.

   Input and Output File

•      fgetc (INPUT)

•       Read one character from a file

•       fgetc(stdin) equivalent with getchar()

•       Syntax : int fgetc( FILE *stream );

•       Return the character when successful, and EOF while error

•      fputc (OUTPUT)

•       Writing one character to a file

•       fputc('a', stdout) similar with putchar( 'a' )

•       Syntax: int fputc( int c, FILE *stream );

•       Return a character when successful, and EOF if error

•      fgets (INPUT)

•       Syntax: char *fgets( char *string, int n, FILE *stream );

•       Read one line from a file that ended with new line, or at maximum of n-1 number of character.

•       Return a string if successful and NULL while error

•      fputs (OUTPUT)

•       Writing a line to a file

•       Syntax: int fputs( const char *string, FILE *stream );

•       Return non-negative value while successful and EOF if error.

•      fscanf  (INPUT)

–      Syntax:

                int fscanf( FILE *stream, const char *format [, argument ]... );

–      Read data from file inline with the scanf formatting.

–      Return the number of field read while successful, and EOF if error

•      fprintf (OUTPUT)

–      Syntax:

                int fprintf( FILE *stream, const char *format [, argument ]...);

–      Writing data to a file using the printf format.

–      Return number of byte written if successful and negative value if error.

–     fwrite

–      syntax: size_t fwrite( const void *buffer, size_t size, size_t count, FILE *stream );

–      Writing a block of data in the buffer area to the file

–      Return number of byte data written, and error otherwise.

–     fread

–      Syntax: size_t fread( void *buffer, size_t size, size_t count, FILE *stream );

–      Read a block size of data from a file

–     feof

–      Syntax : int feof( FILE *stream );

–      Finding out if the pointer has reached end-of-file

–      Return 0 if not end-of-file

   Summary

–      Stream is a sequence of character. All input and output data is a stream. C sees file as a stream.

–      File Definition

–      File is a collection of record

–      Record is a collection of field

–      Field is a block of byte

–      Byte is collection of bit

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Kevin Orlando Sutanto