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Truncate a file: Difference between revisions
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</lang>
=={{header|Icon}} and {{header|Unicon}}==
Unicon provides the built-in function truncate which can be used to truncate a file. The following line of code truncates ''filename'' to ''newsizeinbytes''. The file is opened for both read and write in untranslated mode.
<lang Unicon>truncate(f := open(filename, "bu"), newsizeinbytes) & close(f)</lang>
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}
}</lang>
=={{header|OCaml}}==▼
The <code>Unix</code> module provided with the standard distribution provides a function <code>[http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#VALtruncate truncate]</code>:▼
<lang ocaml>val truncate : string -> int -> unit▼
(** Truncates the named file to the given size. *)</lang>▼
There is also a function <code>[http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#VALftruncate ftruncate]</code> that does the equivalent operation but with a file descriptor instead of a file name:▼
<lang ocaml>val ftruncate : file_descr -> int -> unit▼
(** Truncates the file corresponding to the given descriptor to the given size. *)</lang>▼
=={{header|Liberty BASIC}}==
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</lang>
▲=={{header|OCaml}}==
▲The <code>Unix</code> module provided with the standard distribution provides a function <code>[http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#VALtruncate truncate]</code>:
=={{header|PureBasic}}==▼
PureBasic has the internal function [http://www.purebasic.com/documentation/file/truncatefile.html TruncateFile] that cuts the file at the current file position and discards all data that follows.▼
▲<lang ocaml>val truncate : string -> int -> unit
<lang PureBasic>Procedure SetFileSize(File$, length.q)▼
▲(** Truncates the named file to the given size. *)</lang>
Protected fh, pos, i▼
If FileSize(File$) < length▼
▲There is also a function <code>[http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#VALftruncate ftruncate]</code> that does the equivalent operation but with a file descriptor instead of a file name:
Debug "File to small, is a directory or does not exist."▼
ProcedureReturn #False▼
▲<lang ocaml>val ftruncate : file_descr -> int -> unit
Else ▼
▲(** Truncates the file corresponding to the given descriptor to the given size. *)</lang>
fh = OpenFile(#PB_Any, File$)▼
FileSeek(fh, length)▼
=={{header|Pascal}}==
TruncateFile(fh)▼
<lang pascal>
CloseFile(fh)▼
Program FileTruncate;
EndIf▼
ProcedureReturn #True▼
uses
EndProcedure</lang>▼
SysUtils;
var
myfile: file of byte;
filename: string;
position: integer;
begin
write('File for truncation: ');
readln(filename);
if not FileExists(filename) then
begin
writeln('Error: File does not exist.');
exit;
end;
write('Truncate position: ');
readln(position);
Assign(myfile, filename);
Reset(myfile);
if FileSize(myfile) < position then
begin
writeln('Warning: The file "', filename, '" is too short. No need to truncate at position ', position);
Close(myfile);
exit;
end;
Seek(myfile, position);
Truncate(myfile);
Close(myfile);
writeln('File "', filename, '" truncated at position ', position, '.');
end.
</lang>
Output:
<pre>
File for truncation: test
Truncate position: 3
File "test" truncated at position 3.
</pre>
=={{header|Perl}}==
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<lang PicoLisp>(de truncate (File Len)
(call "truncate" "-s" Len File) )</lang>
▲=={{header|PureBasic}}==
▲PureBasic has the internal function [http://www.purebasic.com/documentation/file/truncatefile.html TruncateFile] that cuts the file at the current file position and discards all data that follows.
▲<lang PureBasic>Procedure SetFileSize(File$, length.q)
▲ Protected fh, pos, i
▲ If FileSize(File$) < length
▲ Debug "File to small, is a directory or does not exist."
▲ ProcedureReturn #False
▲ Else
▲ fh = OpenFile(#PB_Any, File$)
▲ FileSeek(fh, length)
▲ TruncateFile(fh)
▲ CloseFile(fh)
▲ EndIf
▲ ProcedureReturn #True
▲EndProcedure</lang>
=={{header|Python}}==
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