File I/O in Every Programming Language [closed]

LOLCODE

The specs are sketchy to say the least, but I did the best I could. Let the downvoting begin! :) I still find it a fun exercise.

HAI
CAN HAS STDIO?
PLZ OPEN FILE "FILEIO.TXT" ITZ "TehFilez"?
    AWSUM THX
        BTW #There is no standard way to output to files yet...
        VISIBLE "Hello" ON TehFilez
        BTW #There isn't a standard way to append to files either...
        MOAR VISIBLE "World" ON TehFilez
        GIMMEH LINES TehLinez OUTTA TehFilez
        I HAS A SecondLine ITZ 1 IN MAH TehLinez
        VISIBLE SecondLine
    O NOES
        VISIBLE "OH NOES!!!"
KTHXBYE

Python 3

with open('fileio.txt', 'w') as f:
   f.write('hello')
with open('fileio.txt', 'a') as f:
   f.write('\nworld')
with open('fileio.txt') as f:
   s = f.readlines()[1]
print(s)

Clarifications

• readlines() returns a list of all the lines in the file. Therefore, the invokation of readlines() results in reading each and every line of the file. In that particular case it's fine to use readlines() because we have to read the entire file anyway (we want its last line). But if our file contains many lines and we just want to print its nth line, it's unnecessary to read the entire file. Here are some better ways to get the nth line of a file in Python: What substitutes xreadlines() in Python 3?.

• What is this with statement? The with statement starts a code block where you can use the variable f as a stream object returned from the call to open(). When the with block ends, python calls f.close() automatically. This guarantees the file will be closed when you exit the with block no matter how or when you exit the block (even if you exit it via an unhandled exception). You could call f.close() explicitly, but what if your code raises an exception and you don't get to the f.close() call? That's why the with statement is useful.

• You don't need to reopen the file before each operation. You can write the whole code inside one with block.

  with open('fileio.txt', 'w+') as f:
      f.write('hello')
      f.write('\nworld')
      s = f.readlines()[1]
  print(s)
  

  I used three with blocks to emphsize the difference between the three operations: write (mode 'w'), append (mode 'a'), read (mode 'r', the default).

Brain***k

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COBOL

Since nobody else did......

IDENTIFICATION DIVISION.
PROGRAM-ID.  WriteDemo.
AUTHOR.  Mark Mullin.
* Hey, I don't even have a cobol compiler

ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT StudentFile ASSIGN TO "STUDENTS.DAT"
        ORGANIZATION IS LINE SEQUENTIAL.

DATA DIVISION.
FILE SECTION.
FD TestFile.
01 TestData.
   02  LineNum        PIC X.
   02  LineText       PIC X(72).

PROCEDURE DIVISION.
Begin.
    OPEN OUTPUT TestFile
    DISPLAY "This language is still around."

    PERFORM GetFileDetails
    PERFORM UNTIL TestData = SPACES
       WRITE TestData 
       PERFORM GetStudentDetails
    END-PERFORM
    CLOSE TestFile
    STOP RUN.

GetFileDetails.
    DISPLAY "Enter - Line number, some text"
    DISPLAY "NXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
    ACCEPT  TestData.

Haskell

main :: IO ()
main = let filePath = "fileio.txt" in
       do writeFile filePath "hello"
          appendFile filePath "\nworld"
          fileLines <- readFile filePath
          let secondLine = (lines fileLines) !! 1
          putStrLn secondLine

If you just want to read/write a file:

main :: IO ()
main = readFile "somefile.txt" >>= writeFile "someotherfile.txt"