Truncate a file: Difference between revisions

=={{header|C++}}==

<lang C++>#include <string>

#include <fstream>

using namespace std;

void truncateFile(string filename, int max_size) {

std::ifstream input( filename, std::ios::binary );

char buffer;

string outfile = filename + ".trunc";

ofstream appendFile(outfile, ios_base::out);

for(int i=0; i<max_size; i++) {

input.read( &buffer, sizeof(buffer) );

appendFile.write(&buffer,1);

}

appendFile.close(); }

int main () {

truncateFile("test.txt", 5);

return 0;

}

</lang>

=={{header|Go}}==

Go has the required function in the standard library. The implementation calls operating system specific functions and returns whatever errors the operating system reports.

<lang go>import (

"fmt"

"os"

)

if err := os.Truncate("filename", newSize); err != nil {

fmt.Println(err)

}</lang>

Package os also has a separate function that operates on an open file.

=={{header|Perl 6}}==

{{Works with|rakudo|2016.07}}

<lang perl6>use NativeCall;

sub truncate(Str, int32 --> int32) is native {*}

sub MAIN (Str $file, Int $to) {

given $file.IO {

.e or die "$file doesn't exist";

.w or die "$file isn't writable";

.s >= $to or die "$file is not big enough to truncate";

}

truncate($file, $to) == 0 or die "Truncation was unsuccessful";

}</lang>

The external <code>truncate</code> routine could be replaced with the following line (in which case no need for <code>NativeCall</code>):

<lang perl6>spurt $file, slurp($file).substr($to);</lang>

=={{header|Powershell}}==

<lang powershell>Function Truncate-File(fname) {

$null | Set-Content -Path "$fname"

}

</lang>