File.truncate(file_name, integer)  → 0

Truncates the file file_name to be at most integer bytes long. Not available on all platforms.

f = File.new("out", "w")
f.write("1234567890")     #=> 10
f.close                   #=> nil
File.truncate("out", 5)   #=> 0
File.size("out")          #=> 5

Source Code

/*
*  call-seq:
*     File.truncate(file_name, integer)  => 0
*  
*  Truncates the file <i>file_name</i> to be at most <i>integer</i>
*  bytes long. Not available on all platforms.
*     
*     f = File.new("out", "w")
*     f.write("1234567890")     #=> 10
*     f.close                   #=> nil
*     File.truncate("out", 5)   #=> 0
*     File.size("out")          #=> 5
*     
*/

static VALUE
rb_file_s_truncate(klass, path, len)
   VALUE klass, path, len;
{
   off_t pos;

   rb_secure(2);
   pos = NUM2OFFT(len);
   SafeStringValue(path);

#ifdef HAVE_TRUNCATE
   if (truncate(StringValueCStr(path), pos) < 0)
       rb_sys_fail(RSTRING(path)->ptr);
#else
# ifdef HAVE_CHSIZE
   {
       int tmpfd;

#  ifdef _WIN32
       if ((tmpfd = open(StringValueCStr(path), O_RDWR)) < 0) {
           rb_sys_fail(RSTRING(path)->ptr);
       }
#  else
       if ((tmpfd = open(StringValueCStr(path), 0)) < 0) {
           rb_sys_fail(RSTRING(path)->ptr);
       }
#  endif
       if (chsize(tmpfd, pos) < 0) {
           close(tmpfd);
           rb_sys_fail(RSTRING(path)->ptr);
       }
       close(tmpfd);
   }
# else
   rb_notimplement();
# endif
#endif
   return INT2FIX(0);
}