This should be trivial.  However, I've not found in the documentation (trying both std.stdio and std.file) how to write to a file in the manner here:

filename.writefln("%s\t%f", someString, someDouble);

... this merely prints filename to screen ... does not create a data file.

On Wed, 06 Oct 2010 22:43:42 +0400, Dr. Smith <iam@far.out> wrote:

> This should be trivial.  However, I've not found in the documentation (trying
> both std.stdio and std.file) how to write to a file in the manner here:
>
> filename.writefln("%s\t%f", someString, someDouble);
>
> ... this merely prints filename to screen ... does not create a data file.

In your case, foo.bar(args) == bar(foo, args) - that is call Uniform Function Call Syntax, that is:

filename.writefln("%s\t%f", someString, someDouble); -> writefln(filename, "%s\t%f", someString, someDouble);

which in turn tries using filename as a format.

Try using std.stream. It should be something like this:

File file = new File(fileName, FileMode.OutNew); // open file for writing, create new if none exists
file.writefln("hello, %s!", "world");

Not tested but should work.

Here's a minimal little template (checked):

import std.stdio;

void main()
{
        auto f = File("outfile.txt", "w");
        f.writefln("%s World", "Hello");
        f.close();
}





2010/10/6 Denis Koroskin <2korden@gmail.com>

> On Wed, 06 Oct 2010 22:43:42 +0400, Dr. Smith <iam@far.out> wrote:
>
>  This should be trivial.  However, I've not found in the documentation
>> (trying
>> both std.stdio and std.file) how to write to a file in the manner here:
>>
>> filename.writefln("%s\t%f", someString, someDouble);
>>
>> ... this merely prints filename to screen ... does not create a data file.
>>
>
> In your case, foo.bar(args) == bar(foo, args) - that is call Uniform
> Function Call Syntax, that is:
>
> filename.writefln("%s\t%f", someString, someDouble); -> writefln(filename,
> "%s\t%f", someString, someDouble);
>
> which in turn tries using filename as a format.
>
> Try using std.stream. It should be something like this:
>
> File file = new File(fileName, FileMode.OutNew); // open file for writing,
> create new if none exists
> file.writefln("hello, %s!", "world");
>
> Not tested but should work.
>

Thank you.  Indeed, I forgot: auto f = File("outfile.txt", "w");

Interestingly, this apparently works within a for-loop to overwrite the file on the first iteration and appending otherwise (Should there not be an explicit append arg?):

for(int i = 0; i < 100; i++) {
  f.writefln("%s%i", "World Hello", i);
} f.close();                 // f.close outside the loop for efficiency?

If someone could point me to the online documentation for this matter, I'd appreciate it.  I'd prefer to use this forum for less elementary matters.

Dr. Smith Wrote:

> Thank you.  Indeed, I forgot: auto f = File("outfile.txt", "w");
> 
> Interestingly, this apparently works within a for-loop to overwrite the file on the first iteration and appending otherwise (Should there not be an explicit append arg?):
> 
> for(int i = 0; i < 100; i++) {
>   f.writefln("%s%i", "World Hello", i);
> } f.close();                 // f.close outside the loop for efficiency?
> 
> If someone could point me to the online documentation for this matter, I'd appreciate it.  I'd prefer to use this forum for less elementary matters.

auto f = File("name", "options");

Creates a new File object which, based on the options, opens the file for writing (create and replace), reading (binary or text), or appending. All operations are performed on this open file until closed and reopened. So for your example if you do not wish to append to an open file you can do this



Now you can get the same behavior even if you close the File with:

for(int i = 0; i < 100; i++) {
    auto f = File("name.txt", "a");
    f.writefln("%s%i", "World Hello", i);
    f.close();
}

Notice the "a" instead of "w" This is appending to the file when it opens it. Thus the reason the first example has f.close outside the loop is because it is opening the File outside the loop.

http://digitalmars.com/d/2.0/phobos/std_file.html

On Thu, 07 Oct 2010 01:36:23 +0400, Dr. Smith <iam@far.out> wrote:

> Thank you.  Indeed, I forgot: auto f = File("outfile.txt", "w");
>
> Interestingly, this apparently works within a for-loop to overwrite the file on
> the first iteration and appending otherwise (Should there not be an explicit
> append arg?):
>

That's a correct behavior. See how it works: when you open a file, you a get a "pointer" into that file. Every time you write N bytes to that file, your pointer advances the same amount. E.g.

file.write("aaa");
file.write("bbb");

is essentially the same as:

file.write("aaabbb");

If that is not that you want, then you need to store you pointer before writing, and seek back afterwards:

(I don't know the proper syntax so that is a pseudo-code)
auto pos = file.tell();
file.write("aaa");
file.seek(pos);
file.write("bbb");

In this case, you will first write "aaa" to file and then overwrite it with "bbb".

That's the way file I/O works in every OS I know of and that's probably because that's the way hard disks work in general.

Hope that helps.