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## -*- texinfo -*-
## @deftypefn {} {@var{out} =} tar_is_bsd ()
## True if the default tar command is BSD tar.
##
## Checks whether the default tar command (the one invoked when an un-prefixed
## @code{tar} is executed) is BSD tar or another tar.  Caches the results for
## performance.
##
## Returns true if the detected tar is BSD tar, and false otherwise.  Errors if
## @code{tar --version} does not succeed.
## @end deftypefn

function out = tar_is_bsd ()

  ## BSD tar needs to be handled differently from GNU tar
  persistent cache;
  if (isempty (cache))
    [status, tar_ver_str] = system ("tar --version");
    if (status)
      error ("tar: Failed executing tar --version (status = %d)", status);
    endif
    cache = ! isempty (regexp (tar_ver_str, "bsdtar"));
  endif
  out = cache;

endfunction