CS201-18 - Introduction to Programming Lecture 18 File...

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Unformatted text preview: Introduction to Programming Lecture 18 File Types of Files Text Files Executable Programs Memory is volatile Any data that you key in by keyboard while a program is running is also volatile File Handling Text files handling Binary files handling Steps to handle file Open the File Read / Write the File Close the File Streams fstream.h Header File for File Handling Header File for File Handling #include <fstream.h> Input File Stream ifstream Output file stream ofstream Example 1 #include <fstream.h> ifstream myFile ; myFile.open ( “payRoll.txt” ) ; Fully Qualified Path Name C:\myProg\payRoll.txt Access file data myfile >> var1; We can also write: myfile >> var1 >> var2 ; Close the File myFile.close ( ) ; Process : Open myfile.open ( “payRoll.txt” ) ; myFile payRoll.txt Process: Close myfile.close ( “payRoll.txt” ) ; myFile X payRoll.txt Example 1 ifstream myFile ; myFile.open ( “myFile.txt” ) ; if ( !myFile ) // Error check { cout << “Your file could not be opened”; } ­­­­­­ myFile.close ( ) ; Output File Modes Create a new file Overwrite an existing file Append some text Randomly accessing a file Syntax fStream fileVar ( “fileName” , mode ) ; // Generic syntax Opening Mode ifstream myfile ( “myfile.txt” , ios :: in ) ; Opening Mode ofstream myfile ( “myfile.txt” , ios :: out ) ; List of File Handling Modes ios :: in open for reading (default for ifstream) ios :: out open for writing (default for ofstream) ios :: app start writing at end of file (APPend) ios :: ate start reading or writing at EOF of file (ATEnd) ios :: trunc truncate file to zero length if it exists (TRUNCate) ios :: nocreate error when opening if file does not already exist ios :: noreplace error when opening for output if file already exists ios :: binary open file in binary (not text) mode Append ofstream myfile (“myfile.txt” , ios :: app ) ; Random Access ofstream myfile ( “myfile.txt” , ios :: ate ) ; Truncate ofstream myfile ( “myfile.txt” , ios::trunc ) ; myfile.eof ( ) while ( !myfile.eof ( ) ) { myfile >> varName ; } get ( ) char ch ; myFile.get ( ch ) ; Example 2 while ( !myFile.eof ( ) ) { myFile.get ( ch ) ; cout << ch ; } put ( ) outputFile.put ( ch ) ; ifstream myInputFile ( “myfile.txt” , ios :: in ) ; ofstream myOnputFile ( “myfile.txt” , ios :: out ) ; int i ; i = 0 ; int i = 0 ; Open file ifstream myInputFile ( “myfile.txt” ) ; Open file ofstream myOnputFile ( “myfile.txt” ) ; strtok ( ) getline ( ) function Syntax of getline function Character array Numbers of characters to be read myfile.getline (char *s, int n, char delim); delimiter Syntax of getline function Input Hello World myfile.getline ( arrayString , 20 , ’W’ ) ; Output Hello File Amir 1000 Amara 1002 strtok ( string , delimiter ) Example char * namePtr , *salaryPtr , arr [ 30 ] ; double fSalary = 0.0 ; inFile.getline ( arr , 30 , ‘\n’ ) ; namePtr = strtok ( arr , " " ) ; salaryPtr = strtok ( NULL , " " ) ; fSalary = atof ( salaryPtr ) ; : ...
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