Ch8 file processing

Chapter 8 FILE PROCCESSING 8.1 Introduction 8.2 Introduction to File I/O 8.2.1 declaring FILE variables 8.2.2 opening a Disk Files for I/O file open verification 8.2.3 reading and writing to Disk File 8.2.4 closing a Disk Files 8.2.5 EOF

8.1 Introduction Why have files : Large volume of i/p or o/p data More permanent storage of data Transfer to other programs Multiple simultaneous i/p and o/p output streams Data Files Business Data: customer files, payroll files, … Scientific Data: weather data, environmental data, topographic maps, … Image Data: web images, satellite images, medical images, … Web Data: HTML, GIF, JPEG, PNG, XML, …

8.1 Introduction (cont..) Data Files : a named collection of records. normally kept in external storage. C can process 2 types of files : (i) Text files (ii) Binary files

8.1 Introduction (cont..) 3 basic operations : (i) create file (ii) edit file (iii) read data from file

8.2 Introduction to file I/O Steps to work with file Begin declare variable to be of type file fopen( ) function perform I/O fclose ( ) End

8.2.1 Declaring FILE variable Declaring a file pointer variable : FILE *fp ; uppercase fp is a pointer to a file fp data_file

/*a program that able to read name & age and print the data in data file named biodata.dat*/ #include<stdio.h> void main() { FILE *failnama; failnama=fopen("c:\\biodata2.dat","w"); char nama[20]; int umur; fputs("Nama\t umur\n",failnama); fputs("=========================\n",failnama); for(int i=0;i<=3;i++) { printf("Nama:"); scanf("%s",nama); printf("Umur:"); scanf("%d",&umur); fprintf(failnama,"%s\t %d\n",nama,umur); } fclose(failnama); }

use fopen( ) to open a specified file. fp = fopen(filename, mode) e.g : FILE *fp; fp = fopen(“c:\\biodata.dat”, “w”); fp biodata.xls 8.2.2 Opening a File, fopen previous sourcecode

8.2.2 Opening a File (cont..) FILE *fp; fp = fopen(“c:\\biodata.xls”, “w”); Will open the disk file biodata.xls for writing

8.2.2 Opening a File (cont..) Table: 8.1 Filename and mode Read & write, but append instead of overwrite “ a+” Open file to write, but append instead of overwrite “ a” Read & Write, do not destroy file if it exists “ r+” Open file to read “ r” Read & write, but overwrite file if it exists “ w+” Open file to write (create a file) “ w” description Mode

mode (r) /*a program that read the data from biodata.dat*/ #include<stdio.h> void main(){ char nama[30]; int umur; FILE *failnama; failnama=fopen("c:\\biodata.dat","r"); printf("Nama\t umur\n"); printf("--------------------\n"); for(int i=0;i<=3;i++) { fscanf(failnama,"%s\t %d\n",nama,&umur); printf("%s\t %d\n",nama,umur); } fclose(failnama); }

mode (a) //a program that able to append the data into biodata.dat #include<stdio.h> void main(){ FILE *failnama1; FILE *failnama2; failnama1=fopen("c:\\biodata.dat","a+"); failnama2=fopen(“c:\\student.xls”,”w+”); char nama[20]; int umur; for(int i=0;i<=2;i++) { printf("Nama:"); scanf("%s",nama); printf("Umur:"); scanf("%d",&umur); fprintf(failnama1,"%s\t %d\n",nama,umur); fprintf(failnama2,"%s\t %d\n",nama,umur); } fclose(failnama1); fclose(failnama2); }

#include <stdio.h> void main () { FILE *failnama; failnama=fopen("c:\\buku2.xls","w"); struct book_info { int book_no; int year; int edition; double price; } book; for(int i=0;i<=1;i++){ printf("\nBOOK NUMBER : "); scanf("%d",&book.book_no); printf("\nYEAR OF PUBLISHED : "); scanf("%d",&book.year); printf("\nEDITION : "); scanf("%d",&book.edition); printf("\nPRICE : RM "); scanf("%lf",&book.price); } for(i=0;i<=1;i++) { printf("\nBOOK NUMBER : %d", book.book_no); printf("\nYEAR OF PUBLISHED : %d", book.year); printf("\nEDITION : %d", book.edition); printf("\nPRICE : RM %.2lf\n", book.price); } for(i=0;i<=1;i++) { fprintf(failnama,"book number: %d\t year: %d\t edition: %d\t price: %.2f\n",book.book_no,book.year,book.edition,book.price); } fclose(failnama); }

fopen returns NULL if the file could not be opened in the mode requested. When the file cannot be opened, a suitable error message is displayed. File open verification

File open verification (cont..) #include<stdio.h> #define NULL 0 void main( ) { char nama[30]; int umur; FILE *failnama; failnama = fopen("c:\\biodata.dat","r+"); if (failnama == NULL) printf("\n ERROR - Can't open the file\n"); else { printf("Nama\tumur\n"); printf("--------------------\n"); for(int i=0;i<=3;i++) { fscanf(failnama,"%s\t %d\n",nama,&umur); printf("%s\t %d\n",nama,umur); } } fclose(failnama); }

8.2.3 Writing to Disk File Prototype: fprintf(FILE *fp,output_format,variable); e.g fprintf(fp,”%s %d\n” , name,age); previous sourcecode

fputs( ) #include<stdio.h> FILE *fp; void main(){ fp=fopen("c:\\menteri.xls","w");//Bina fail baru fputs("Abdullah Badawi\n",fp); fputs("Najib Razak\n",fp); fputs("Muhyiddin Yassin\n",fp); fputs("Azmi Khalid\n",fp); fclose(fp);//tutup fail }

8.2.3 Reading to Disk File Prototype: fscanf(FILE *fp,input_format,address of variable); e.g fscanf(fp,”%s %d\n” , &name,&age); previous sourcecode

fgets( ) #include <stdio.h> #include <string.h> void main ( ) { FILE *filePtr; char person[100]; int bil; filePtr=fopen("menteri.dat","r"); /*baca string dari fail*/ for (bil=1;bil<=7;bil++) { fgets(person,strlen(person),filePtr); puts(person); } fclose(filePtr); }

8.2.4 Closing a Disk File fclose() function closes the file that was opened by a call to the fopen() function Statement: fclose(fp); fp is a pointer file variable

End of File (EOF) eof marker is operating system defined & indicate no more data is to be read. windows <ctrl> z returns 0 if eof not found. otherwise, returns 1.

End of File (EOF) (cont..) #include<stdio.h> #define NULL 0 void main( ) { char nama[30]; int umur; FILE *pelajar; pelajar = fopen("c:\\biodata2.dat","w+"); if (pelajar == NULL) printf("\n ERROR - Can't open the file\n"); else{ printf("Enter eof to end input\n"); printf("Nama\tumur\n"); printf("--------------------\n"); //while not end of file while ( ! feof( stdin ) ) { fprintf( pelajar, "%s %d \n", nama, umur ); printf("Nama:"); scanf("%s",nama); printf("Umur:"); scanf("%d",&umur); }//end while fclose(pelajar); }//end else }

Ch8 file processing

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Ch8 file processing