File I/O in Every Programming Language [closed]

Question

This has to be a common question that all programmers have from time to time. How do I read a line from a text file? Then the next question is always how do i write it back.

Of course most of you use a high level framework in day to day programming (which are fine to use in answers) but sometimes it's nice to know how to do it at a low level too.

I myself know how to do it in C, C++ and Objective-C, but it sure would be handy to see how it's done in all of the popular languages, if only to help us make a better decision about what language to do our file io in. In particular I think it would be interesting to see how its done in the string manipulation languages, like: python, ruby and of course perl.

So I figure here we can create a community resource that we can all star to our profiles and refer to when we need to do file I/O in some new language. Not to mention the exposure we will all get to languages that we don't deal with on a day to day basis.

This is how you need to answer:

1. Create a new text file called "fileio.txt"
2. Write the first line "hello" to the text file.
3. Append the second line "world" to the text file.
4. Read the second line "world" into an input string.
5. Print the input string to the console.

Clarification:

• You should show how to do this in one programming language per answer only.
• Assume that the text file doesn't exist beforehand
• You don't need to reopen the text file after writing the first line

No particular limit on the language. C, C++, C#, Java, Objective-C are all great.

If you know how to do it in Prolog, Haskell, Fortran, Lisp, or Basic then please go right ahead.

Answer 1

Scala:

Using standard library:

val path = "fileio.txt"
val fout = new FileWriter(path)
fout write "hello\n"
fout.close()
val fout0 = new FileWriter(path, true)
fout0 write "world\n"
fout0.close() 
val str = Source.fromFile(path).getLines.toSeq(1)
println(str)

Using Josh Suereth's Scala-ARM Library:

val path = "fileio.txt"
for(fout <- managed(new FileWriter(path))) 
  fout write "hello\n"
for(fout <- managed(new FileWriter(path, true))) 
  fout write "world\n"
val str = Source.fromFile(path).getLines.toSeq(1)
println(str)      

---

---

Since many people have used the same file descriptor to write the two strings, I'm also including that way in my answer.

Using standard library:

val path = "fileio.txt"
val fout = new FileWriter(path)
fout write "hello\n"
fout write "world\n"
fout.close()
val str = Source.fromFile(path).getLines.toSeq(1)
println(str)

Using Josh Suereth's Scala-ARM Library:

val path = "fileio.txt"
for(fout <- managed(new FileWriter(path))){
  fout write "hello\n"
  fout write "world\n"
}
val str = Source.fromFile(path).getLines.toSeq(1)
println(str)

Answer 2

D

module d_io;

import std.stdio;


void main()
{
    auto f = File("fileio.txt", "w");
    f.writeln("hello");
    f.writeln("world");

    f.open("fileio.txt", "r");
    f.readln;
    auto s = f.readln;
    writeln(s);
}

Answer 3

Shell Script (UNIX)

#!/bin/sh
echo "hello" > fileio.txt
echo "world" >> fileio.txt
LINE=`sed -ne2p fileio.txt`
echo $LINE

Actually the sed -n "2p" part prints the second line, but the question asks for the second line to be stored in a variable and then printed, so... :)

Answer 4

PHP

<?php

$filePath = "fileio.txt";

file_put_contents($filePath, "hello");
file_put_contents($filePath, "\nworld", FILE_APPEND);

$lines = file($filePath);

echo $lines[1];

// closing PHP tags are bad practice in PHP-only files, don't use them

Answer 5

Brain***k

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Answer 6

Common Lisp

(defun main ()
  (with-open-file (s "fileio.txt" :direction :output :if-exists :supersede)
    (format s "hello"))
  (with-open-file (s "fileio.txt" :direction :io :if-exists :append)
    (format s "~%world")
    (file-position s 0)
    (loop repeat 2 for line = (read-line s nil nil) finally (print line))))