Writing State Information to a File
Last updated: April 30, 2025
File handling in various programming languages
#include
int main()
{
FILE *read;
FILE *write;
char *filename = "myfile.txt";
read = fopen( filename, "r" );
if( read == NULL )
{
//File doesn't exist. Have to write something
write = fopen( filename, "w" );
fprintf( write, "%s", "writesomethinghere" );
fclose( write );
}
else
{
//File exists. Read data from the file
char somedata[ 20 ];
fscanf( read, "%s", somedata );
printf( "%s", somedata );
fclose( read );
}
return 0;
}
#include
#include
#include
using namespace std;
int main()
{
ifstream readfile;
ofstream writefile;
string filename = "myfile.txt";
readfile.open( filename.c_str() );
if( readfile )
{
//I can read something from the file
readfile.close();
}
else
{
//The file doesn't exist
writefile.open( filename.c_str() );
//write something to the file
writefile << " write some data " << endl;
writefile.close();
}
return 0;
}
import java.io.*;
import java.lang.*;
public class Solution
{
public static void main( String[] args )
{
File fileName = new File( "myfile.txt" );
if( !fileName.exists() )
{
System.out.println( "this file doesn't exist " );
try
{
fileName.createNewFile();
FileWriter fileWrite = new FileWriter( fileName );
BufferedWriter bufferedWriter = new BufferedWriter( fileWrite );
//bufferedWriter.write( "write something here " );
bufferedWriter.close();
} catch ( IOException e )
{
//catch exception
}
}
else
{
//System.out.println( "this file exists " );
try
{
byte[] buffer = new byte[ 100 ];
FileInputStream inputStream = new FileInputStream( fileName );
int readLines = -1;
while( ( readLines = inputStream.read( buffer ) ) != -1 )
{
//System.out.println( new String( buffer ) );
}
inputStream.close();
} catch ( IOException e )
{
//catch exception
}
}
}
}
using System;
using System.IO;
public class Solution
{
public static void Main( )
{
string fileName = "myfile.txt";
FileStream file = new FileStream( fileName, FileMode.OpenOrCreate, FileAccess.Read );
StreamReader sr = new StreamReader( file );
string s = sr.ReadToEnd();
if( string.IsNullOrEmpty( s ) )
{
file.Close();
//The file is empty. Write something to it
//Console.WriteLine( "file doesn't exist " );
file = new FileStream( fileName, FileMode.OpenOrCreate, FileAccess.Write );
StreamWriter sw = new StreamWriter( file );
sw.Write( "Write something here " );
sw.Close();
}
else
{
//Console.WriteLine( s );
}
}
}
#!/usr/bin/python
filename = "myfile.txt"
with open( filename ) as f:
# file read can happen here
# print "file exists"
print f.readlines()
with open( filename, "w") as f:
# print "file write happening here"
f.write("write something here ")
#!/usr/bin/env ruby
filename = "myfile.txt"
if File.exist?( filename )
#puts "file read happening"
f = File.open(filename, 'r')
data = f.read
puts data
end
f = File.open(filename, 'a+')
#puts "file write happening"
f.puts "write something here"
$filename = "myfile.txt";
if(file_exists($filename)) {
$data = file_get_contents( $filename );
print $data;
$filewrite = fopen( $filename, 'a') or die('Cannot open file:'.$filename);
fwrite( $filewrite, "write something here");
fclose( $filewrite );
} else {
$filewrite = fopen( $filename, 'w') or die('Cannot open file:'.$filename);
fwrite( $filewrite, "write something here");
fclose( $filewrite );
}
?>#!/usr/bin/env perl
$filename = "myfile.txt";
if( -e $filename )
{
unless(open FILE, $filename)
{
die "Cannot open file";
}
while(my $line =)
{
print $line;
}
close FILE;
}
unless(open FILE, '>>'.$filename)
{
die "Cannot open file";
}
print FILE "Write something here";
close FILE;