Re: How can I easily determine the last charachter of a file?

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On Tuesday, 14 February 2023 at 18:30:05 UTC, seany wrote:

Hello

Consider the content of a file

````
First line \n
Second line ....
....
data data data data  ... last char

````

My goal is to find out whether the last character is a new line or not. Please not, it will be sufficient if this works on Linux.

More specifically I want to insert a new line at the end of the file. File.writeline inserts a line at the end of the _newly added line_.

Thus if I had


````
First line \n
Second line ....
....
data data data data  ... non-NL-char

````

and wanted to insert : `newline-word-word-word ... non-NLchar`

Via `file.writeln`, it would end up as

````
First line \n
Second line ....
....

data data data data ... non-NL-char{no newline or whitespace here}Newline-word-word-word ... non-NLchar{newline}

````

This is not unexpected. But, I want to make sure, that my appending automatically adds a new line. However, it should not add empty lines.

One brute force method is to copy every line of the file to a temp file or in the RAM and then write back in the original file. I would like to avoid that if possible.

Thanks.

Building on previous response:

module test;
@safe:

import std;

void main()
{
    File myFile =  "somefile.txt";
    myFile.seek(-1, SEEK_END);

    ubyte[1] c;
    () @trusted { myFile.rawRead(c[]); } ();

    if(ControlChar.lf == c[0]) // is this portable??
        writeln("yep, last char is a linefeed.");
    else
        writeln("nope. last char is not a linefeed.");

}