Assigns a new ID code to a dataset; this is useful when making
a copy of a dataset, so that the internal ID codes remain unique.

Usage: 3dnewid dataset [dataset ...]
       3dnewid -fun [n]
       to see what n randomly generated ID codes look like.
       (If the integer n is not present, 1 ID code is printed.)
       3dnewid -fun11
       to get an 11 character ID code (for use in scripting).
       3dnewid -int
       to get a random positive integer.
       The values are usually between 1 million and 1 billion.
       Such a value could be used as a random seeds in various AFNI
       programs, such as 3dttest++ -seed.
       3dnewid -hash STR
       to get a unique hashcode of STR
       (Unlike the other ways of using 3dnewid, if STR is the)
       (same in 2 different runs, the output will be the same.)
       (The -hash algorithm begins at step 2 in the list below.)
       3dnewid -MD5 STR
       to get the MD5 hash of STR, should be same as -hash output
       without the prefix and without the + and / char substitutions.

How ID codes are created (here and in other AFNI programs):
The AFNI ID code generator attempts to create a globally unique
string identifier, using the following steps.
1) A long string is created from the system identifier
   information ('uname -a'), the current epoch time in seconds
   and microseconds, the process ID, and the number of times
   the current process has called the ID code function.
2) This string is then hashed into a 128 bit code using the
   MD5 algorithm. (cf. file thd_md5.c)
3) This bit code is then converted to a 22 character string
   using Base64 encoding, replacing '/' with '-' and '+' with '_'.
   With these changes, the ID code can be used as a Unix filename
   or an XML name string. (cf. file thd_base64.c)
4) A 4 character prefix is attached at the beginning to produce
   the final ID code.  If you set the environment variable
   IDCODE_PREFIX to something, then its first 3 characters and an
   underscore will be used for the prefix of the new ID code,
   provided that the first character is alphabetic and the other
   2 alphanumeric; otherwise, the default prefix 'NIH_' will be
The source code is function UNIQ_idcode() in file niml_uuid.c

++ Compile date = May  7 2021 {AFNI_21.1.06:linux_ubuntu_16_64}