Programming-in-D-in-Chinese
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files.html

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<title>Files</title>
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Files</h4>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
We have seen in the previous chapter that standard input and output streams can
be redirected to and from files and other programs with the<code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">&gt;</code>,<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">&lt;</code>,
and<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">|</code><span class="Apple-converted-space">&nbsp;</span>operators
on the console. Despite being very powerful, these tools are not suitable in
every situation because in many cases programs can not complete their tasks by
reading from their input and writing to their output like a simple pipe.</p>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
For example, a program that deals with student records may use its standard
output to display the program menu. Such a program would need to write the
student records to an actual file instead of<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">stdout</code>.</p>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
In this chapter, we will cover reading from and writing to files of file
systems.</p>
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Fundamental concepts</h5>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
Files are represented by the<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">File</code><span class="Apple-converted-space">&nbsp;</span><i style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">struct</i><span class="Apple-converted-space">&nbsp;</span>of
the<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">std.stdio</code><span class="Apple-converted-space">&nbsp;</span>module.
Since I haven&#39;t introduced structs yet, we will have to accept the syntax of
struct construction as-is for now.</p>
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Before getting to code samples we have to go through fundamental concepts about
files.</p>
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The producer and the consumer</h6>
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Files that are created on one platform may not be readily usable on other
platforms. Merely opening a file and writing data in it may not be sufficient
for that data to be available on the consumer&#39;s side. The producer and the
consumer of the data must have already agreed on the format of the data that is
in the file. For example, if the producer has written the id and the name of the
student records in a certain order, the consumer must read the data back in the
same order.</p>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
Additionally, the sample codes below do not write BOM to the beginning of the
file. This may make your files incompatible with systems that require BOM. (BOM
is short for<span class="Apple-converted-space">&nbsp;</span><i style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">byte
order mark</i>. It specifies in what order the UTF code units of characters are
arranged in a file.)</p>
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Access rights</h6>
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File systems present files to programs under certain access rights. Access
rights are important for both data integrity and performance.</p>
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When it is about reading, allowing multiple programs read from the same file
would improve performance because no program would be waiting for any other to
finish their reading. On the other hand, when it is about writing, only one
program should be allowed to write to a file, otherwise programs may overwrite
each other&#39;s data.</p>
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Opening a file</h6>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
The standard input and output streams<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">stdin</code><span class="Apple-converted-space">&nbsp;</span>and<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">stdout</code><span class="Apple-converted-space">&nbsp;</span>are
already<i style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">open</i><span class="Apple-converted-space">&nbsp;</span>when
programs start running. They are ready to be used.</p>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
On the other hand, files must first be opened by specifying the name of the file
and the access rights that are needed.</p>
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Closing a file</h6>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
Any file that has been opened by a program must be closed when the program
finishes using that file. In most cases the files need not be closed explicitly;
they are closed automatically when<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">File</code><span class="Apple-converted-space">&nbsp;</span>objects
are terminated automatically:</p>
<pre class="d_code" style="margin: 0.5em 1em 0.75em 16px; padding: 0.5em; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 1em; vertical-align: baseline; background-color: rgb(255, 255, 255); color: rgb(0, 0, 0); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;"><span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: blue; background-position: initial initial; background-repeat: initial initial;">if</span> (aCondition) {

    <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: green; background-position: initial initial; background-repeat: initial initial;">// Assume a File object has been created and used here.
</span>    <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: green; background-position: initial initial; background-repeat: initial initial;">// ...
</span>
} <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: green; background-position: initial initial; background-repeat: initial initial;">// ← The actual file would be closed automatically here
</span>  <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: green; background-position: initial initial; background-repeat: initial initial;">//   when leaving this scope. No need to close explicitly.
</span></pre>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
In some cases a file object may need to be re-opened to access a different file
or the same file with different access rights. In such cases the file must be
closed and re-opened:</p>
<pre class="d_code" style="margin: 0.5em 1em 0.75em 16px; padding: 0.5em; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 1em; vertical-align: baseline; background-color: rgb(255, 255, 255); color: rgb(0, 0, 0); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">    file.close();
    file.open(<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;student_records&quot;</span>, <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;r&quot;</span>);
</pre>
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Writing to and reading from files</h6>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
Since files are character streams, input and output functions<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">writeln</code>,<code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">readf</code>,
etc. are used exactly the same way with them. The only difference is that the
name of the<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">File</code><span class="Apple-converted-space">&nbsp;</span>variable
and a dot must be typed:</p>
<pre class="d_code" style="margin: 0.5em 1em 0.75em 16px; padding: 0.5em; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 1em; vertical-align: baseline; background-color: rgb(255, 255, 255); color: rgb(0, 0, 0); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">    writeln(<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;hello&quot;</span>);        <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: green; background-position: initial initial; background-repeat: initial initial;">// writes to standard output
</span>    stdout.writeln(<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;hello&quot;</span>); <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: green; background-position: initial initial; background-repeat: initial initial;">// same as above
</span>    <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: rgb(255, 255, 136); background-position: initial initial; background-repeat: initial initial;">file.</span>writeln(<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;hello&quot;</span>);   <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: green; background-position: initial initial; background-repeat: initial initial;">// writes to the specified file
</span></pre>
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<code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">
eof()</code><span class="Apple-converted-space">&nbsp;</span>to determine the end of
a file</h6>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
The<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">eof()</code><span class="Apple-converted-space">&nbsp;</span>member
function determines whether the end of a file has been reached while reading
from a file. It returns<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">true</code><span class="Apple-converted-space">&nbsp;</span>if
the end of the file has been reached.</p>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
For example, the following loop will be active until the end of the file:</p>
<pre class="d_code" style="margin: 0.5em 1em 0.75em 16px; padding: 0.5em; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 1em; vertical-align: baseline; background-color: rgb(255, 255, 255); color: rgb(0, 0, 0); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">    <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: blue; background-position: initial initial; background-repeat: initial initial;">while</span> (!file.eof()) {
        <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: green; background-position: initial initial; background-repeat: initial initial;">/* ... */</span>
    }
</pre>
<h6 style="margin: 1.25em 0.5em 0.5em 8px; padding: 0px; border: 0px; outline: 0px; font-size: 1.1em; vertical-align: baseline; background-color: transparent; font-family: sans-serif; font-weight: bold; color: rgb(0, 0, 51); font-style: normal; font-variant: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
The<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">std.file</code><span class="Apple-converted-space">&nbsp;</span>module</h6>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
The<span class="Apple-converted-space">&nbsp;</span><a href="http://dlang.org/phobos/std_file.html" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: purple; text-decoration: none; background-position: initial initial; background-repeat: initial initial;"><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: purple; background-position: initial initial; background-repeat: initial initial;">std.file</code><span class="Apple-converted-space">&nbsp;</span>module</a><span class="Apple-converted-space">&nbsp;</span>contains
functions and types that are useful when working with contents of directories.
For example,<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">exists</code><span class="Apple-converted-space">&nbsp;</span>can
be used to determine whether a file or a directory exists on the file systems:</p>
<pre class="d_code" style="margin: 0.5em 1em 0.75em 16px; padding: 0.5em; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 1em; vertical-align: baseline; background-color: rgb(255, 255, 255); color: rgb(0, 0, 0); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;"><span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: blue; background-position: initial initial; background-repeat: initial initial;">import</span> std.file;

<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: green; background-position: initial initial; background-repeat: initial initial;">// ...
</span>
    <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: blue; background-position: initial initial; background-repeat: initial initial;">if</span> (exists(fileName)) {
        <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: green; background-position: initial initial; background-repeat: initial initial;">// there is a file or directory under that name
</span>
    } <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: blue; background-position: initial initial; background-repeat: initial initial;">else</span> {
        <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: green; background-position: initial initial; background-repeat: initial initial;">// no file or directory under that name
</span>    }
</pre>
<h5 style="margin: 1.25em 0.5em 0.5em 8px; padding: 0px; border: 0px; outline: 0px; font-size: 1.25em; vertical-align: baseline; background-color: transparent; font-family: sans-serif; font-weight: bold; color: rgb(0, 0, 51); font-style: normal; font-variant: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
<code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">
std.stdio.File</code><span class="Apple-converted-space">&nbsp;</span>struct</h5>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
<code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">
File</code><span class="Apple-converted-space">&nbsp;</span>uses the same mode
characters that are used by<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">fopen</code><span class="Apple-converted-space">&nbsp;</span>of
the C programming language:</p>
<table border="1" cellpadding="4" cellspacing="0" style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; color: rgb(0, 0, 0); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;" width="570">
	<tbody style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
		<tr align="center" style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<th scope="col" style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			&nbsp;Mode&nbsp;</th>
			<th scope="col" style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			Definition</th>
		</tr>
		<tr style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<td align="center" style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<tt style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
			r</tt></td>
			<td style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<b style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
			read</b><span class="Apple-converted-space">&nbsp;</span>access<br />
			the file is opened to be read from the beginning</td>
		</tr>
		<tr style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<td align="center" style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<tt style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
			r+</tt></td>
			<td style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<b style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
			read and write</b><span class="Apple-converted-space">&nbsp;</span>access<br />
			the file is opened to be read from and written at the beginning</td>
		</tr>
		<tr style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<td align="center" style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<tt style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
			w</tt></td>
			<td style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<b style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
			write</b><span class="Apple-converted-space">&nbsp;</span>access<br />
			if the file does not exist, it is created as empty<br />
			if the file already exists, its contents are cleared</td>
		</tr>
		<tr style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<td align="center" style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<tt style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
			w+</tt></td>
			<td style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<b style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
			read and write</b><span class="Apple-converted-space">&nbsp;</span>access<br />
			if the file does not exist, it is created as empty<br />
			if the file already exists, its contents are cleared</td>
		</tr>
		<tr style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<td align="center" style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<tt style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
			a</tt></td>
			<td style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<b style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
			append</b><span class="Apple-converted-space">&nbsp;</span>access<br />
			if the file does not exist, it is created as empty<br />
			if the file already exists, its contents are preserved and it is
			opened to be written at the end</td>
		</tr>
		<tr style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<td align="center" style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<tt style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
			a+</tt></td>
			<td style="margin: 1em; padding: 0px; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; font-family: monospace; background-position: initial initial; background-repeat: initial initial;">
			<b style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
			read and append</b><span class="Apple-converted-space">&nbsp;</span>access<br />
			if the file does not exist, it is created as empty<br />
			if the file already exists, its contents are preserved and the file
			is opened to be read from the beginning and written at the end</td>
		</tr>
</table>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
A &#39;b&#39; character may be added to the mode string as in &quot;rb&quot;. This may have an
effect on platforms that support the<span class="Apple-converted-space">&nbsp;</span><i style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">binary
mode</i>, but it is ignored on all POSIX systems.</p>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
The<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">File</code><span class="Apple-converted-space">&nbsp;</span>struct
is included in the<span class="Apple-converted-space">&nbsp;</span><a href="http://dlang.org/phobos/std_stdio.html" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: purple; text-decoration: none; background-position: initial initial; background-repeat: initial initial;"><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: purple; background-position: initial initial; background-repeat: initial initial;">std.stdio</code><span class="Apple-converted-space">&nbsp;</span>module</a>.</p>
<h6 style="margin: 1.25em 0.5em 0.5em 8px; padding: 0px; border: 0px; outline: 0px; font-size: 1.1em; vertical-align: baseline; background-color: transparent; font-family: sans-serif; font-weight: bold; color: rgb(0, 0, 51); font-style: normal; font-variant: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
Writing to a file</h6>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
The file must have been opened in one of the write modes first:</p>
<pre class="d_code" style="margin: 0.5em 1em 0.75em 16px; padding: 0.5em; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 1em; vertical-align: baseline; background-color: rgb(255, 255, 255); color: rgb(0, 0, 0); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;"><span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: blue; background-position: initial initial; background-repeat: initial initial;">import</span> std.stdio;

<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: blue; background-position: initial initial; background-repeat: initial initial;">void</span> main()
{
    File file = File(<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;student_records&quot;</span>, <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: rgb(255, 255, 136); background-position: initial initial; background-repeat: initial initial;"><span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;w&quot;</span></span>);

    file.writeln(<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;Name  : &quot;</span>, <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;Zafer&quot;</span>);
    file.writeln(<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;Number: &quot;</span>, 123);
    file.writeln(<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;Class : &quot;</span>, <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;1A&quot;</span>);
}
</pre>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
As you remember from the<span class="Apple-converted-space">&nbsp;</span><a href="http://ddili.org/ders/d.en/strings.html" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: purple; text-decoration: none; background-position: initial initial; background-repeat: initial initial;">Strings
chapter</a>, the type of literals like<span class="d_string" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;"><tt style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">&quot;student_records&quot;</tt></span><span class="Apple-converted-space">&nbsp;</span>is<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">string</code>,
consisting of immutable characters. For that reason, it is not possible to
construct<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">File</code><span class="Apple-converted-space">&nbsp;</span>objects
by a mutable file name (e.g.<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">char[]</code>).
When needed, it would be necessary to call the<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">.idup</code><span class="Apple-converted-space">&nbsp;</span>property
of the mutable string.</p>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
The program above creates or overwrites the contents of a file named<code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">student_records</code><span class="Apple-converted-space">&nbsp;</span>in
the directory that it has been started under (in the program&#39;s<span class="Apple-converted-space">&nbsp;</span><i style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">working
directory</i>).</p>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
<i style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
<b style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
Note:</b><span class="Apple-converted-space">&nbsp;</span>File names can contain any
character that is legal for that file system. To be portable, I will use only
ASCII characters.</i></p>
<h6 style="margin: 1.25em 0.5em 0.5em 8px; padding: 0px; border: 0px; outline: 0px; font-size: 1.1em; vertical-align: baseline; background-color: transparent; font-family: sans-serif; font-weight: bold; color: rgb(0, 0, 51); font-style: normal; font-variant: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
Reading from a file</h6>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
The file must have been opened in one of the read modes first:</p>
<pre class="d_code" style="margin: 0.5em 1em 0.75em 16px; padding: 0.5em; border: 1px dotted rgb(153, 204, 153); outline: 0px; font-size: 1em; vertical-align: baseline; background-color: rgb(255, 255, 255); color: rgb(0, 0, 0); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;"><span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: blue; background-position: initial initial; background-repeat: initial initial;">import</span> std.stdio;
<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: blue; background-position: initial initial; background-repeat: initial initial;">import</span> std.string;

<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: blue; background-position: initial initial; background-repeat: initial initial;">void</span> main()
{
    File file = File(<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;student_records&quot;</span>, <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: rgb(255, 255, 136); background-position: initial initial; background-repeat: initial initial;"><span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;r&quot;</span></span>);

    <span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: blue; background-position: initial initial; background-repeat: initial initial;">while</span> (!file.eof()) {
        string line = chomp(file.readln());
        writeln(<span style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 13px; vertical-align: baseline; background-color: transparent; color: red; background-position: initial initial; background-repeat: initial initial;">&quot;read line -&gt; |&quot;</span>, line);
    }
}
</pre>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
The program above reads all of the lines of the file named<code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">student_records</code><span class="Apple-converted-space">&nbsp;</span>and
prints those lines to its standard output.</p>
<h5 style="margin: 1.25em 0.5em 0.5em 8px; padding: 0px; border: 0px; outline: 0px; font-size: 1.25em; vertical-align: baseline; background-color: transparent; font-family: sans-serif; font-weight: bold; color: rgb(0, 0, 51); font-style: normal; font-variant: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
Exercise</h5>
<ul style="margin: 0.5em 1em 1em; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
	<li style="margin: 0.5em 0px 0px 1em; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
	Write a program that takes a file name from the user, opens that file, and
	writes all of the non-empty lines of that file to another file. The name of
	the new file can be based on the name of the original file. For example, if
	the original file is<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">foo.txt</code>,
	the new file can be<span class="Apple-converted-space">&nbsp;</span><code class="d_inline" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 1.2em; vertical-align: baseline; background-color: transparent; font-weight: bold; color: rgb(0, 34, 34); background-position: initial initial; background-repeat: initial initial;">foo.txt.out</code>.</li>
</ul>
<p style="margin: 0.75em 1em 0.75em 16px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: rgb(0, 0, 0); font-family: serif; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 19px; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-position: initial initial; background-repeat: initial initial;">
<a href="http://ddili.org/ders/d.en/files.cozum.html" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; color: purple; text-decoration: none; background-position: initial initial; background-repeat: initial initial;" target="ddili_cozum">
<i style="margin: 0px; padding: 0px; border: 0px; outline: 0px; font-size: 16px; vertical-align: baseline; background-color: transparent; background-position: initial initial; background-repeat: initial initial;">
... the solution</i></a></p>
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