的大小argv受操作系统限制，并且因操作系统而异。引用Linux手册execve(2)页：

Limits on size of arguments and environment
   Most Unix implementations impose some limit on the total size
   of the command-line argument (argv) and environment (envp)
   strings that may be passed to a new program.  POSIX.1 allows an
   implementation to advertise this limit using the ARG_MAX
   constant (either defined in <limits.h> or available at run time
   using the call sysconf(_SC_ARG_MAX)).

   On Linux prior to kernel 2.6.23, the memory used to store the
   environment and argument strings was limited to 32 pages
   (defined by the kernel constant MAX_ARG_PAGES).  On
   architectures with a 4-kB page size, this yields a maximum size
   of 128 kB.

   On kernel 2.6.23 and later, most architectures support a size
   limit derived from the soft RLIMIT_STACK resource limit (see
   getrlimit(2)) that is in force at the time of the execve()
   call.  (Architectures with no memory management unit are
   excepted: they maintain the limit that was in effect before
   kernel 2.6.23.)  This change allows programs to have a much
   larger argument and/or environment list.  For these
   architectures, the total size is limited to 1/4 of the allowed
   stack size.  (Imposing the 1/4-limit ensures that the new
   program always has some stack space.)  Since Linux 2.6.25, the
   kernel places a floor of 32 pages on this size limit, so that,
   even when RLIMIT_STACK is set very low, applications are
   guaranteed to have at least as much argument and environment
   space as was provided by Linux 2.6.23 and earlier.  (This
   guarantee was not provided in Linux 2.6.23 and 2.6.24.)
   Additionally, the limit per string is 32 pages (the kernel
   constant MAX_ARG_STRLEN), and the maximum number of strings is
   0x7FFFFFFF.