
read(+Stream, -Term)

   Succeeds if the next term from the input stream Stream is successfully read
and unified with Term.



Arguments
   Stream              Integer (stream number) or Atom (reserved or user-defined                symbolic stream name).
   Term                Prolog term or variable.

Type
   Term I/O

Description
   Used to read the next term from the input stream Stream and unify it
   with Term.  If there is more than one Prolog term in the file, the term
   must be in Prolog term format i.e.  terminated by fullstop (a period and
   a blank space character), neither of which are retained by Prolog.


   Otherwise, end of file acts like fullstop.  If only end of file is read,
   the event 190 is raised and the default handler unifies Term with the
   atom end_of_file.


   The default action for syntax errors is to print a warning and fail.




Modes and Determinism
   read(+, -) is semidet

Modules
   This predicate is sensitive to its module context (tool predicate, see @/2).

Fail Conditions
   Fails if a syntax error was detected and no term could be read

Exceptions
     4 --- Stream is not instantiated.
     5 --- Stream is not an atom or an integer.
   190 --- End of file was encountered before reading any character.
   192 --- Stream is not an input stream.
   193 --- Stream is an illegal stream specification.
   198 --- Trying to read even after the error 190 was raised.

Examples
   
Success:
      [eclipse]: read(0,Term).
      > atom.
      Term = atom
      yes.

      [eclipse]: open(file1,write,s),write(s, 'f(1,2,3).\ng(1,2'),
      > write(s, ',3). h(1,2,3).\ni.\nj(1, 2\n,3).').
      yes.
      [eclipse]: system('cat file1').
      f(1,2,3).
      g(1,2,3). h(1,2,3).
      i.
      j(1, 2
      ,3).
      yes.
      [eclipse]: open(file1,read,s), read(s,A), read(s,B),
      > read(s,C), read(s,D), read(s,E), read(s,F).
      A = f(1, 2, 3)
      B = g(1, 2, 3)
      C = h(1, 2, 3)
      D = i
      E = j(1, 2, 3)
      F = end_of_file
      yes.
Fail:
      [eclipse]: read(0,a).
      > b.
      no.

      [eclipse]: read(0,X).
      > f(1,2)m.
              ^ (here?)
      syntax error: postfix/infix operator expected
      no (more) solution.
Error:
      read(a(b,c),S).               (Error 4).
      read("string", a(b,c)).       (Error 5).
      read(9, X=2).                 (Error 192). % stream not open
      read(atom, X=2).              (Error 193).





See Also
   read / 1, readvar / 3, read_token / 2, read_token / 3
