array.shift   →   obj or nil

Returns the first element of self and removes it (shifting all other elements down by one). Returns nil if the array is empty.

args = [ "-m", "-q", "filename" ]
args.shift   #=> "-m"
args         #=> ["-q", "filename"]

Source Code

/*
*  call-seq:
*     array.shift   ->   obj or nil
*  
*  Returns the first element of <i>self</i> and removes it (shifting all
*  other elements down by one). Returns <code>nil</code> if the array
*  is empty.
*     
*     args = [ "-m", "-q", "filename" ]
*     args.shift   #=> "-m"
*     args         #=> ["-q", "filename"]
*/

VALUE
rb_ary_shift(ary)
   VALUE ary;
{
   VALUE top;

   rb_ary_modify_check(ary);
   if (RARRAY(ary)->len == 0) return Qnil;
   top = RARRAY(ary)->ptr[0];
   if (RARRAY_LEN(ary) < ARY_DEFAULT_SIZE && !FL_TEST(ary, ELTS_SHARED)) {
       MEMMOVE(RARRAY_PTR(ary), RARRAY_PTR(ary)+1, VALUE, RARRAY_LEN(ary)-1);
   }
   else {
       if (!FL_TEST(ary, ELTS_SHARED)) {
           RARRAY(ary)->ptr[0] = Qnil;
       }
       ary_make_shared(ary);
       RARRAY(ary)->ptr++;            /* shift ptr */
   }
   RARRAY(ary)->len--;

   return top;
}