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gvpr (1)

Name

gvpr - graph pattern scanning and processing language ( previously known as gpr )

Synopsis

gvpr  [-icqV?]   [  -o outfile ] [ -a args ] [ 'prog' | -f progfile ] [
files ]

Description

GVPR(1)                     General Commands Manual                    GVPR(1)



NAME
       gvpr - graph pattern scanning and processing language
       ( previously known as gpr )

SYNOPSIS
       gvpr  [-icqV?]   [  -o outfile ] [ -a args ] [ 'prog' | -f progfile ] [
       files ]

DESCRIPTION
       gvpr is a graph stream editor inspired by awk.  It copies input  graphs
       to  its  output,  possibly transforming their structure and attributes,
       creating new graphs, or  printing  arbitrary  information.   The  graph
       model  is that provided by libcgraph(3).  In particular, gvpr reads and
       writes graphs using the dot language.

       Basically, gvpr traverses each input graph,  denoted  by  $G,  visiting
       each  node  and  edge, matching it with the predicate-action rules sup-
       plied in the input program.  The rules are  evaluated  in  order.   For
       each  predicate  evaluating  to  true, the corresponding action is per-
       formed.  During the traversal, the current node or edge  being  visited
       is denoted by $.

       For  each  input graph, there is a target subgraph, denoted by $T, ini-
       tially empty and used to accumulate  chosen  entities,  and  an  output
       graph,  $O,  used  for final processing and then written to output.  By
       default, the output graph is the target graph.  The output graph can be
       set in the program or, in a limited sense, on the command line.

OPTIONS
       The following options are supported:

       -a args
              The  string args is split into whitespace-separated tokens, with
              the individual tokens available as strings in the  gvpr  program
              as  ARGV[0],...,ARGV[ARGC-1].  Whitespace characters within sin-
              gle or double quoted substrings, or preceded by a backslash, are
              ignored  as separators.  In general, a backslash character turns
              off any special meaning of the following character.   Note  that
              the tokens derived from multiple -a flags are concatenated.

       -c     Use the source graph as the output graph.

       -i     Derive  the  node-induced subgraph extension of the output graph
              in the context of its root graph.

       -o outfile
              Causes the output stream to be written to the specified file; by
              default, output is written to stdout.

       -f progfile
              Use the contents of the specified file as the program to execute
              on the input. If progfile contains a slash character,  the  name
              is  taken  as the pathname of the file. Otherwise, gvpr will use
              the directories specified in the environment variable GPRPATH to
              look  for  the file. If -f is not given, gvpr will use the first
              non-option argument as the program.

       -q     Turns off warning messages.

       -V     Causes the program to print version information and exit.

       -?     Causes the program to print usage information and exit.

OPERANDS
       The following operand is supported:

       files   Names of files containing 1 or more graphs in the dot language.
               If  no  -f  option is given, the first name is removed from the
               list and used as the input program. If the  list  of  files  is
               empty, stdin will be used.

PROGRAMS
       A  gvpr  program consists of a list of predicate-action clauses, having
       one of the forms:

              BEGIN { action }

              BEG_G { action }

              N [ predicate ] { action }

              E [ predicate ] { action }

              END_G { action }

              END { action }

       A program can contain at most one of each of the BEGIN, END_G  and  END
       clauses.   There  can  be  any number of BEG_G, N and E statements, the
       first applied to graphs, the second  to  nodes,  the  third  to  edges.
       These  are  separated  into  blocks,  a block consisting of an optional
       BEG_G statement and all N and E statements up to the next BEG_G  state-
       ment, if any.  The top-level semantics of a gvpr program are:

              Evaluate the BEGIN clause, if any.
              For each input graph G {
                  For each block {
                      Set G as the current graph and current object.
                      Evaluate the BEG_G clause, if any.
                      For each node and edge in G {
                          Set the node or edge as the current object.
                          Evaluate the N or E clauses, as appropriate.
                      }
                  }
                  Set G as the current object.
                  Evaluate the END_G clause, if any.
              }
              Evaluate the END clause, if any.

       The  actions  of  the BEGIN, BEG_G, END_G and END clauses are performed
       when the clauses are evaluated.  For N or E clauses, either the  predi-
       cate  or  action  may  be  omitted.   If  there is no predicate with an
       action, the action is performed on every node or edge, as  appropriate.
       If  there is no action and the predicate evaluates to true, the associ-
       ated node or edge is added to the target graph.

       The blocks are evaluated in the order in which they  occur.   Within  a
       block,  the  N  clauses  (E clauses, respectively) are evaluated in the
       order in which the occur. Note, though, that within a  block,  N  or  E
       clauses may be interlaced, depending on the traversal order.

       Predicates  and  actions  are  sequences of statements in the C dialect
       supported by the expr(3) library.  The only difference  between  predi-
       cates  and  actions is that the former must have a type that may inter-
       preted as either true or false.  Here the usual C  convention  is  fol-
       lowed, in which a non-zero value is considered true. This would include
       non-empty strings and non-empty references to nodes, edges,  etc.  How-
       ever, if a string can be converted to an integer, this value is used.

       In  addition  to  the usual C base types (void, int, char, float, long,
       unsigned and double), gvpr provides string as a synonym for char*,  and
       the  graph-based  types  node_t,  edge_t, graph_t and obj_t.  The obj_t
       type can be viewed as a supertype of the other 3  concrete  types;  the
       correct base type is maintained dynamically.  Besides these base types,
       the only other supported type expressions are (associative) arrays.

       Constants follow C syntax, but strings may be quoted with either  "..."
       or '...'.  gvpr accepts C++ comments as well as cpp-type comments.  For
       the latter, if a line begins with a '#' character, the rest of the line
       is ignored.

       A statement can be a declaration of a function, a variable or an array,
       or an executable statement. For declarations, there is a single  scope.
       Array declarations have the form:

               type array [ type0 ]

       where   type0   is optional. If it is supplied, the parser will enforce
       that all array subscripts have the specified type. If it  is  not  sup-
       plied,  objects of all types can be used as subscripts.  As in C, vari-
       ables and arrays must be declared. In particular, an  undeclared  vari-
       able will be interpreted as the name of an attribute of a node, edge or
       graph, depending on the context.

       Executable statements can be one of the following:
              { [ statement ... ] }
              expression              // commonly var = expression
              if( expression ) statement [ else statement ]
              for( expression ; expression ; expression ) statement
              for( array [ var ]) statement
              forr( array [ var ]) statement
              while( expression ) statement
              switch( expression ) case statements
              break [ expression ]
              continue [ expression ]
              return [ expression ]
       Items in brackets are optional.

       In the second form of the for statement and  the  forr  statement,  the
       variable  var  is  set  to each value used as an index in the specified
       array and then the associated statement is evaluated. For  numeric  and
       string  indices,  the  indices  are returned in increasing (decreasing)
       numeric or lexicographic order for for (forr, respectively).  This  can
       be used for sorting.

       Function definitions can only appear in the BEGIN clause.

       Expressions  include the usual C expressions.  String comparisons using
       == and != treat the right hand operand as a pattern for the purpose  of
       regular  expression  matching.   Patterns use ksh(1) file match pattern
       syntax.  (For simple string equality, use the strcmp function.

       gvpr will attempt to use an expression as a string or numeric value  as
       appropriate.  Both  C-like casts and function templates will cause con-
       versions to be performed, if possible.

       Expressions of graphical type (i.e., graph_t,  node_t,  edge_t,  obj_t)
       may  be followed by a field reference in the form of .name. The result-
       ing value is the value of the attribute named name of the given object.
       In  addition,  in certain contexts an undeclared, unmodified identifier
       is taken to be an attribute name. Specifically, such identifiers denote
       attributes  of  the  current  node  or  edge,  respectively, in N and E
       clauses, and the current graph in BEG_G and END_G clauses.

       As usual in the libcgraph(3) model, attributes are  string-valued.   In
       addition, gvpr supports certain pseudo-attributes of graph objects, not
       necessarily string-valued. These reflect intrinsic  properties  of  the
       graph objects and cannot be set by the user.

       head : node_t
              the head of an edge.

       tail : node_t
              the tail of an edge.

       name : string
              the  name of an edge, node or graph. The name of an edge has the
              form "<tail-name><edge-op><head-name>[<key>]",  where  <edge-op>
              is  "->"  or  "--" depending on whether the graph is directed or
              not. The bracket part [<key>] only appears if  the  edge  has  a
              non-trivial key.

       indegree : int
              the indegree of a node.

       outdegree : int
              the outdegree of a node.

       degree : int
              the degree of a node.

       root : graph_t
              the root graph of an object. The root of a root graph is itself.

       parent : graph_t
              the  parent  graph  of a subgraph. The parent of a root graph is
              NULL

       n_edges : int
              the number of edges in the graph

       n_nodes : int
              the number of nodes in the graph

       directed : int
              true (non-zero) if the graph is directed

       strict : int
              true (non-zero) if the graph is strict

BUILT-IN FUNCTIONS
       The following functions are built into gvpr. Those functions  returning
       references to graph objects return NULL in case of failure.

   Graphs and subgraph
       graph(s : string, t : string) : graph_t
              creates  a  graph whose name is s and whose type is specified by
              the string t. Ignoring case, the characters U, D, S, N have  the
              interpretation  undirected,  directed,  strict,  and non-strict,
              respectively. If t is empty, a  directed,  non-strict  graph  is
              generated.

       subg(g : graph_t, s : string) : graph_t
              creates  a  subgraph  in  graph  g  with name s. If the subgraph
              already exists, it is returned.

       isSubg(g : graph_t, s : string) : graph_t
              returns the subgraph in graph g with name s, if  it  exists,  or
              NULL otherwise.

       fstsubg(g : graph_t) : graph_t
              returns the first subgraph in graph g, or NULL if none exists.

       nxtsubg(sg : graph_t) : graph_t
              returns the next subgraph after sg, or NULL.

       isDirect(g : graph_t) : int
              returns true if and only if g is directed.

       isStrict(g : graph_t) : int
              returns true if and only if g is strict.

       nNodes(g : graph_t) : int
              returns the number of nodes in g.

       nEdges(g : graph_t) : int
              returns the number of edges in g.

   Nodes
       node(sg : graph_t, s : string) : node_t
              creates  a  node  in  graph  g of name s. If such a node already
              exists, it is returned.

       subnode(sg : graph_t, n : node_t) : node_t
              inserts the node n into the subgraph g. Returns the node.

       fstnode(g : graph_t) : node_t
              returns the first node in graph g, or NULL if none exists.

       nxtnode(n : node_t) : node_t
              returns the next node after n in the root graph, or NULL.

       nxtnode_sg(sg : graph_t, n : node_t) : node_t
              returns the next node after n in sg, or NULL.

       isNode(sg : graph_t, s : string) : node_t
              looks for a node in (sub)graph sg of name  s.  If  such  a  node
              exists, it is returned. Otherwise, NULL is returned.

       isSubnode(sg : graph_t, n : node_t) : int
              returns  non-zero  if node n is in (sub)graph sg, or zero other-
              wise.

       indegreeOf(sg : graph_t, n : node_t) : int
              returns the indegree of node n in (sub)graph sg.

       outdegreeOf(sg : graph_t, n : node_t) : int
              returns the outdegree of node n in (sub)graph sg.

       degreeOf(sg : graph_t, n : node_t) : int
              returns the degree of node n in (sub)graph sg.

   Edges
       edge(t : node_t, h : node_t, s : string) : edge_t
              creates an edge with tail node t, head node h and name s in  the
              root  graph. If the graph is undirected, the distinction between
              head and tail nodes is unimportant.  If  such  an  edge  already
              exists, it is returned.

       edge_sg(sg : graph_t, t : node_t, h : node_t, s : string) : edge_t
              creates  an  edge  with  tail  node t, head node h and name s in
              (sub)graph sg (and all parent graphs). If  the  graph  is  undi-
              rected,  the distinction between head and tail nodes is unimpor-
              tant.  If such an edge already exists, it is returned.

       subedge(g : graph_t, e : edge_t) : edge_t
              inserts the edge e into the subgraph g. Returns the edge.

       isEdge(t : node_t, h : node_t, s : string) : edge_t
              looks for an edge with tail node t, head node h and name  s.  If
              the  graph  is undirected, the distinction between head and tail
              nodes is unimportant.  If such an edge exists, it  is  returned.
              Otherwise, NULL is returned.

       isEdge_sg(sg : graph_t, t : node_t, h : node_t, s : string) : edge_t
              looks  for  an  edge with tail node t, head node h and name s in
              (sub)graph sg. If  the  graph  is  undirected,  the  distinction
              between  head  and  tail  nodes is unimportant.  If such an edge
              exists, it is returned. Otherwise, NULL is returned.

       isSubedge(g : graph_t, e : edge_t) : int
              returns non-zero if edge e is in (sub)graph sg, or  zero  other-
              wise.

       fstout(n : node_t) : edge_t
              returns the first outedge of node n in the root graph.

       fstout_sg(sg : graph_t, n : node_t) : edge_t
              returns the first outedge of node n in (sub)graph sg.

       nxtout(e : edge_t) : edge_t
              returns the next outedge after e in the root graph.

       nxtout_sg(sg : graph_t, e : edge_t) : edge_t
              returns the next outedge after e in graph sg.

       fstin(n : node_t) : edge_t
              returns the first inedge of node n in the root graph.

       fstin_sg(sg : graph_t, n : node_t) : edge_t
              returns the first inedge of node n in graph sg.

       nxtin(e : edge_t) : edge_t
              returns the next inedge after e in the root graph.

       nxtin_sg(sg : graph_t, e : edge_t) : edge_t
              returns the next inedge after e in graph sg.

       fstedge(n : node_t) : edge_t
              returns the first edge of node n in the root graph.

       fstedge_sg(sg : graph_t, n : node_t) : edge_t
              returns the first edge of node n in graph sg.

       nxtedge(e : edge_t, node_t) : edge_t
              returns the next edge after e in the root graph.

       nxtedge_sg(sg : graph_t, e : edge_t, node_t) : edge_t
              returns the next edge after e in the graph sg.

   Graph I/O
       write(g : graph_t) : void
              prints g in dot format onto the output stream.

       writeG(g : graph_t, fname : string) : void
              prints g in dot format into the file fname.

       fwriteG(g : graph_t, fd : int) : void
              prints g in dot format onto the open stream denoted by the inte-
              ger fd.

       readG(fname : string) : graph_t
              returns a graph read from the file fname. The graph should be in
              dot format. If no graph can be read, NULL is returned.

       freadG(fd : int) : graph_t
              returns  the  next  graph read from the open stream fd.  Returns
              NULL at end of file.

   Graph miscellany
       delete(g : graph_t, x : obj_t) : void
              deletes object x from graph g.  If g is NULL, the function  uses
              the  root graph of x.  If x is a graph or subgraph, it is closed
              unless x is locked.

       isIn(g : graph_t, x : obj_t) : int
              returns true if x is in subgraph g.

       cloneG(g : graph_t, s : string) : graph_t
              creates a clone of graph g with name of s.  If s is "", the cre-
              ated graph has the same name as g.

       clone(g : graph_t, x : obj_t) : obj_t
              creates  a clone of object x in graph g.  In particular, the new
              object has the same name/value attributes and structure  as  the
              original  object.   If  an object with the same key as x already
              exists, its attributes are overlaid by those of x and the object
              is  returned.   If an edge is cloned, both endpoints are implic-
              itly cloned.  If a graph is cloned, all nodes,  edges  and  sub-
              graphs  are  implicitly cloned.  If x is a graph, g may be NULL,
              in which case the cloned object will be a  new  root  graph.  In
              this case, the call is equivalent to cloneG(x,"").

       copy(g : graph_t, x : obj_t) : obj_t
              creates  a copy of object x in graph g, where the new object has
              the same name/value attributes as the original  object.   If  an
              object with the same key as x already exists, its attributes are
              overlaid by those of x and the object is  returned.   Note  that
              this  is  a  shallow  copy.  If x is a graph, none of its nodes,
              edges or subgraphs are copied into the new graph.  If  x  is  an
              edge,  the  endpoints are created if necessary, but they are not
              cloned.  If x is a graph, g may  be  NULL,  in  which  case  the
              cloned object will be a new root graph.

       copyA(src : obj_t, tgt : obj_t) : int
              copies  the  attributes of object src to object tgt, overwriting
              any attribute values tgt may initially have.

       induce(g : graph_t) : void
              extends g to its node-induced subgraph  extension  in  its  root
              graph.

       hasAttr(src : obj_t, name : string) : int
              returns  non-zero  if  object src has an attribute whose name is
              name. It returns 0 otherwise.

       isAttr(g : graph_t, kind : string, name : string) : int
              returns non-zero if an attribute name has been defined in g  for
              objects  of  the  given kind. For nodes, edges, and graphs, kind
              should be "N", "E", and "G", respectively.  It returns 0  other-
              wise.

       aget(src : obj_t, name : string) : string
              returns  the value of attribute name in object src. This is use-
              ful for those cases when name conflicts with one of the keywords
              such  as  "head"  or  "root".   If  the  attribute  has not been
              declared in the graph, the function will initialize  it  with  a
              default  value  of "". To avoid this, one should use the hasAttr
              or isAttr function to check that the attribute exists.

       aset(src : obj_t, name : string, value : string) : int
              sets the value  of  attribute  name  in  object  src  to  value.
              Returns 0 on success, non-zero on failure. See aget above.

       getDflt(g : graph_t, kind : string, name : string) : string
              returns  the  default value of attribute name in objects in g of
              the given kind. For nodes, edges, and  graphs,  kind  should  be
              "N",  "E", and "G", respectively.  If the attribute has not been
              declared in the graph, the function will initialize  it  with  a
              default  value  of  "". To avoid this, one should use the isAttr
              function to check that the attribute exists.

       setDflt(g : graph_t, kind : string, name : string, value  :  string)  :
       int
              sets  the default value of attribute name to value in objects in
              g of the given kind. For nodes, edges, and graphs,  kind  should
              be  "N", "E", and "G", respectively.  Returns 0 on success, non-
              zero on failure. See getDflt above.

       fstAttr(g : graph_t, kind : string) : string
              returns the name of the first attribute of objects in g  of  the
              given  kind.  For  nodes, edges, and graphs, kind should be "N",
              "E", and "G", respectively.  If there  are  no  attributes,  the
              string "" is returned.

       nxtAttr(g : graph_t, kind : string, name : string) : string
              returns  the  name  of the next attribute of objects in g of the
              given kind after the attribute name.  The argument name must  be
              the  name  of  an  existing  attribute; it will typically be the
              return value of an previous call to  fstAttr  or  nxtAttr.   For
              nodes,  edges,  and  graphs,  kind  should be "N", "E", and "G",
              respectively.  If there are no attributes left, the string "" is
              returned.

       compOf(g : graph_t, n : node_t) : graph_t
              returns  the  connected component of the graph g containing node
              n, as a subgraph of g. The subgraph only contains the nodes. One
              can  use induce to add the edges. The function fails and returns
              NULL if n is not in g. Connectivity is based on  the  underlying
              undirected graph of g.

       kindOf(obj : obj_t) : string
              returns  an indication of what kind of graph object is the argu-
              ment.  For nodes, edges, and graphs, it returns should  be  "N",
              "E", and "G", respectively.

       lock(g : graph_t, v : int) : int
              implements  graph  locking  on  root graphs. If the integer v is
              positive, the graph is set so that future calls to  delete  have
              no  immediate  effect.   If v is zero, the graph is unlocked. If
              there has been a call to delete the graph while it  was  locked,
              the graph is closed.  If v is negative, nothing is done.  In all
              cases, the previous lock value is returned.

   Strings
       sprintf(fmt : string, ...) : string
              returns the string resulting from formatting the values  of  the
              expressions  occurring after fmt according to the printf(3) for-
              mat fmt

       gsub(str : string, pat : string) : string

       gsub(str : string, pat : string, repl : string) : string
              returns str with all substrings matching pat deleted or replaced
              by repl, respectively.

       sub(str : string, pat : string) : string

       sub(str : string, pat : string, repl : string) : string
              returns  str with the leftmost substring matching pat deleted or
              replaced by repl, respectively. The characters '^' and  '$'  may
              be used at the beginning and end, respectively, of pat to anchor
              the pattern to the beginning or end of str.

       substr(str : string, idx : int) : string

       substr(str : string, idx : int, len : int) : string
              returns the substring of str starting at position idx to the end
              of  the  string or of length len, respectively.  Indexing starts
              at 0. If idx is negative or idx is greater than  the  length  of
              str, a fatal error occurs. Similarly, in the second case, if len
              is negative or idx + len is greater than the length  of  str,  a
              fatal error occurs.

       strcmp(s1 : string, s2 : string) : int
              provides the standard C function strcmp(3).

       index(s : string, t : string) : int

       rindex(s : string, t : string) : int
              returns  the  index of the character in string s where the left-
              most (rightmost) copy of string t can be found, or -1  if  t  is
              not a substring of s.

       match(s : string, p : string) : int
              returns  the  index of the character in string s where the left-
              most match of pattern p can be found, or -1 if no substring of s
              matches p.

       toupper(s : string) : string
              returns  a version of s with the alphabetic characters converted
              to upper-case.

       tolower(s : string) : string
              returns a version of s with the alphabetic characters  converted
              to lower-case.

       canon(s : string) : string
              returns  a  version of s appropriate to be used as an identifier
              in a dot file.

       html(g : graph_t, s : string) : string
              returns a ``magic'' version  of s as an HTML string.  This  will
              typically  be  used  to  attach  an  HTML-like  label to a graph
              object. Note that the returned string lives in g. In particular,
              it will be freed when g is closed, and to act as an HTML string,
              it has to be used with an object of g. In  addition,  note  that
              the  angle bracket quotes should not be part of s. These will be
              added if g is written in concrete DOT format.

       xOf(s : string) : string
              returns the string "x" if s has the form "x,y", where both x and
              y are numeric.

       yOf(s : string) : string
              returns the string "y" if s has the form "x,y", where both x and
              y are numeric.

       llOf(s : string) : string
              returns   the   string   "llx,lly"   if   s   has    the    form
              "llx,lly,urx,ury",  where  all  of  llx,  lly,  urx, and ury are
              numeric.

       urOf(s)
              urOf(s : string) : string returns the string "urx,ury" if s  has
              the  form "llx,lly,urx,ury", where all of llx, lly, urx, and ury
              are numeric.

       sscanf(s : string, fmt : string, ...) : int
              scans the string s, extracting values according to the sscanf(3)
              format  fmt.   The  values are stored in the addresses following
              fmt, addresses having the form &v,  where  v  is  some  declared
              variable  of the correct type.  Returns the number of items suc-
              cessfully scanned.

       split(s : string, arr : array, seps : string) : int

       split(s : string, arr : array) : int

       tokens(s : string, arr : array, seps : string) : int

       tokens(s : string, arr : array) : int
              The split function breaks the string s into  fields,  while  the
              tokens function breaks the string into tokens.  A field consists
              of all non-separator characters between two separator characters
              or  the beginning or end of the string. Thus, a field may be the
              empty string. A token is a maximal, non-empty substring not con-
              taining  a  separator  character.   The separator characters are
              those given in the seps argument.  If seps is not provided,  the
              default  value  is  " \t\n".  The functions return the number of
              fields or tokens.

              The fields and tokens are stored  in  the  argument  array.  The
              array  must be string-valued and, if an index type is specified,
              it must be int. The entries are indexed by consecutive integers,
              starting  at  0.  Any values already stored in the array will be
              either overwritten, or  still  be  present  after  the  function
              returns.

   I/O
       print(...) : void
              print(  expr, ... ) prints a string representation of each argu-
              ment in turn onto stdout, followed by a newline.

       printf(fmt : string, ...) : int

       printf(fd : int, fmt : string, ...) : int
              prints the string resulting from formatting the  values  of  the
              expressions following fmt according to the printf(3) format fmt.
              Returns 0 on success.  By default, it prints on stdout.  If  the
              optional  integer  fd  is  given,  output is written on the open
              stream associated with fd.

       scanf(fmt : string, ...) : int

       scanf(fd : int, fmt : string, ...) : int
              scans in values from an input stream according to  the  scanf(3)
              format  fmt.   The  values are stored in the addresses following
              fmt, addresses having the form &v,  where  v  is  some  declared
              variable  of the correct type.  By default, it reads from stdin.
              If the optional integer fd is given, input is read from the open
              stream associated with fd.  Returns the number of items success-
              fully scanned.

       openF(s : string, t : string) : int
              opens the file s as an I/O stream. The string argument t  speci-
              fies  how  the file is opened. The arguments are the same as for
              the C function fopen(3).  It returns  an  integer  denoting  the
              stream, or -1 on error.

              As  usual, streams 0, 1 and 2 are already open as stdin, stdout,
              and stderr, respectively. Since gvpr may use stdin to  read  the
              input graphs, the user should avoid using this stream.

       closeF(fd : int) : int
              closes the open stream denoted by the integer fd.  Streams  0, 1
              and 2 cannot be closed.  Returns 0 on success.

       readL(fd : int) : string
              returns the next line read from the input stream fd. It  returns
              the  empty string "" on end of file. Note that the newline char-
              acter is left in the returned string.

   Math
       exp(d : double) : double
              returns e to the dth power.

       log(d : double) : double
              returns the natural log of d.

       sqrt(d : double) : double
              returns the square root of the double d.

       pow(d : double, x : double) : double
              returns d raised to the xth power.

       cos(d : double) : double
              returns the cosine of d.

       sin(d : double) : double
              returns the sine of d.

       atan2(y : double, x : double) : double
              returns the arctangent of y/x in the range -pi to pi.

       MIN(y : double, x : double) : double
              returns the minimum of y and x.

       MAX(y : double, x : double) : double
              returns the maximum of y and x.

   Associative Arrays
       # arr : int
              returns the number of elements in the array arr.

       idx in arr : int
              returns 1 if a value has been set for index  idx  in  the  array
              arr.  It returns 0 otherwise.

       unset(v : array, idx) : int
              removes  the  item  indexed  by  idx.  It  returns 1 if the item
              existed, 0 otherwise.

       unset(v : array) : void
              re-initializes the array.

   Miscellaneous
       exit(v : int) : void
              causes gvpr to exit with the exit code v.

       system(cmd : string) : int
              provides the standard C function system(3).  It executes cmd  in
              the user's shell environment, and returns the exit status of the
              shell.

       rand() : double
              returns a pseudo-random double between 0 and 1.

       srand() : int

       srand(v : int) : int
              sets a seed for the random number generator. The optional  argu-
              ment gives the seed; if it is omitted, the current time is used.
              The previous seed value is  returned.  srand  should  be  called
              before any calls to rand.

       colorx(color : string, fmt : string) : string
              translates  a  color from one format to another. The color argu-
              ment should be a color in one of the recognized string represen-
              tations. The fmt value should be one of "RGB", "RGBA", "HSV", or
              "HSVA".  An empty string is returned on error.

BUILT-IN VARIABLES
       gvpr provides certain special, built-in variables, whose values are set
       automatically  by  gvpr  depending on the context. Except as noted, the
       user cannot modify their values.

       $ : obj_t
              denotes the current object (node, edge, graph) depending on  the
              context.  It is not available in BEGIN or END clauses.

       $F : string
              is the name of the current input file.

       $G : graph_t
              denotes  the  current graph being processed. It is not available
              in BEGIN or END clauses.

       $O : graph_t
              denotes the output graph. Before graph traversal, it is initial-
              ized to the target graph. After traversal and any END_G actions,
              if it refers to a non-empty graph, that graph  is  printed  onto
              the  output stream.  It is only valid in N, E and END_G clauses.
              The output graph may be set by the user.

       $T : graph_t
              denotes the current target graph. It is a subgraph of $G and  is
              available only in N, E and END_G clauses.

       $tgtname : string
              denotes  the name of the target graph.  By default, it is set to
              "gvpr_result".  If used multiple times during the  execution  of
              gvpr,  the name will be appended with an integer.  This variable
              may be set by the user.

       $tvroot : node_t
              indicates the starting  node  for  a  (directed  or  undirected)
              depth-first  traversal  of  the  graph (cf. $tvtype below).  The
              default value is NULL for each input graph.

       $tvedge : edge_t
              For BFS and DFS traversals, this is set  to  the  edge  used  to
              arrive  at  the current node or edge. At the beginning of a tra-
              versal, or for other traversal types, the value is NULL.

       $tvtype : tvtype_t
              indicates how gvpr traverses a graph. It can only  take  one  of
              the  constant  values  with  the  previx  "TV_" described below.
              TV_flat is the default.

              In the underlying graph library cgraph(3), edges  in  undirected
              graphs  are  given an arbitrary direction. This is used for tra-
              versals, such as TV_fwd, requiring directed edges.

       ARGC : int
              denotes the number of arguments specified by the  -a  args  com-
              mand-line argument.

       ARGV : string array
              denotes the array of arguments specified by the -a args command-
              line argument. The ith argument is given by ARGV[i].

BUILT-IN CONSTANTS
       There are several symbolic constants defined by gvpr.

       NULL : obj_t
              a null object reference, equivalent to 0.

       TV_flat : tvtype_t
              a simple, flat traversal, with graph objects  visited  in  seem-
              ingly arbitrary order.

       TV_ne : tvtype_t
              a traversal which first visits all of the nodes, then all of the
              edges.

       TV_en : tvtype_t
              a traversal which first visits all of the edges, then all of the
              nodes.

       TV_dfs : tvtype_t
       TV_postdfs : tvtype_t
       TV_prepostdfs : tvtype_t
              a  traversal  of  the  graph  using  a depth-first search on the
              underlying undirected graph.  To do  the  traversal,  gvpr  will
              check  the  value of $tvroot. If this has the same value that it
              had previously (at the start, the previous value is  initialized
              to  NULL.),  gvpr  will  simply look for some unvisited node and
              traverse its connected component. On the other hand, if  $tvroot
              has changed, its connected component will be toured, assuming it
              has not been previously visited or, if $tvroot is NULL, the tra-
              versal will stop. Note that using TV_dfs and $tvroot, it is pos-
              sible to create an infinite loop.

              By default, the traversal is done in pre-order. That is, a  node
              is  visited  before  all of its unvisited edges. For TV_postdfs,
              all of a node's unvisited edges are visited before the node. For
              TV_prepostdfs,  a node is visited twice, before and after all of
              its unvisited edges.

       TV_fwd : tvtype_t
       TV_postfwd : tvtype_t
       TV_prepostfwd : tvtype_t
              A traversal of the graph using a depth-first search on the graph
              following  only  forward arcs.  The choice of roots for the tra-
              versal is the same as described for TV_dfs above.  The different
              order  of visitation specified by TV_fwd, TV_postfwd and TV_pre-
              postfwd are the same as those specified by the analogous traver-
              sals TV_dfs, TV_postdfs and TV_prepostdfs.

       TV_rev : tvtype_t
       TV_postrev : tvtype_t
       TV_prepostrev : tvtype_t
              A traversal of the graph using a depth-first search on the graph
              following only reverse arcs.  The choice of roots for  the  tra-
              versal is the same as described for TV_dfs above.  The different
              order of visitation specified by TV_rev, TV_postrev and  TV_pre-
              postrev are the same as those specified by the analogous traver-
              sals TV_dfs, TV_postdfs and TV_prepostdfs.

       TV_bfs : tvtype_t
              A traversal of the graph using a bread-first search on the graph
              ignoring  edge  directions. See the item on TV_dfs above for the
              role of $tvroot.

EXAMPLES
              gvpr -i 'N[color=="blue"]' file.gv

       Generate the node-induced subgraph of all nodes with color blue.

              gvpr -c 'N[color=="blue"]{color = "red"}' file.gv

       Make all blue nodes red.

              BEGIN { int n, e; int tot_n = 0; int tot_e = 0; }
              BEG_G {
                n = nNodes($G);
                e = nEdges($G);
                printf ("%d nodes %d edges %s0, n, e, $G.name);
                tot_n += n;
                tot_e += e;
              }
              END { printf ("%d nodes %d edges total0, tot_n, tot_e) }

       Version of the program gc.

              gvpr -c ""

       Equivalent to nop.

              BEG_G { graph_t g = graph ("merge", "S"); }
              E {
                node_t h = clone(g,$.head);
                node_t t = clone(g,$.tail);
                edge_t e = edge(t,h,"");
                e.weight = e.weight + 1;
              }
              END_G { $O = g; }

       Produces a  strict  version  of  the  input  graph,  where  the  weight
       attribute  of an edge indicates how many edges from the input graph the
       edge represents.

              BEGIN {node_t n; int deg[]}
              E{deg[head]++; deg[tail]++; }
              END_G {
                for (deg[n]) {
                  printf ("deg[%s] = %d0, n.name, deg[n]);
                }
              }

       Computes the degrees of nodes with edges.

              BEGIN {
                int i, indent;
                int seen[string];
                void prInd (int cnt) {
                  for (i = 0; i < cnt; i++) printf ("  ");
                }
              }
              BEG_G {

                 $tvtype = TV_prepostfwd;
                 $tvroot = node($,ARGV[0]);
              }
              N {
                if (seen[$.name]) indent--;
                else {
                  prInd(indent);
                    print ($.name);
                  seen[$.name] = 1;
                  indent++;
                }
              }

       Prints the depth-first traversal of the graph, starting with  the  node
       whose name is ARGV[0], as an indented list.

ENVIRONMENT
       GPRPATH
              Colon-separated  list  of directories to be searched to find the
              file specified by the -f option.

BUGS AND WARNINGS
       Scripts should be careful deleting nodes  during  N{}  and  E{}  blocks
       using  BFS  and  DFS  traversals  as these rely on stacks and queues of
       nodes.

       When the program is given as a command line argument, the  usual  shell
       interpretation  takes place, which may affect some of the special names
       in gvpr. To avoid this, it is  best  to  wrap  the  program  in  single
       quotes.

       If  string  constants  contain  pattern metacharacters that you want to
       escape to avoid pattern matching, two backslashes will probably be nec-
       essary,  as  a  single backslash will be lost when the string is origi-
       nally scanned. Usually, it is simpler to use strcmp  to  avoid  pattern
       matching.

       As  of  24  April  2008, gvpr switched to using a new, underlying graph
       library, which uses the simpler model that there is only one copy of  a
       node,  not  one  copy  for  each subgraph logically containing it. This
       means that iterators such as InxtnodeP cannot traverse a subgraph using
       just  a node argument. For this reason, subgraph traversal requires new
       functions ending in "_sg", which also take  a  subgraph  argument.  The
       versions without that suffix will always traverse the root graph.

       There  is a single global scope, except for formal function parameters,
       and even these can interfere with the type system. Also, the extent  of
       all  variables  is the entire life of the program.  It might be prefer-
       able for scope to reflect the natural nesting of the  clauses,  or  for
       the  program to at least reset locally declared variables.  For now, it
       is advisable to use distinct names for all variables.

       If a function ends with a complex statement, such as an  IF  statement,
       with  each  branch  doing  a return, type checking may fail.  Functions
       should use a return at the end.

       The expr library does not support  string  values  of  (char*)0.   This
       means  we can't distinguish between "" and (char*)0 edge keys.  For the
       purposes of looking up and  creating  edges,  we  translate  ""  to  be
       (char*)0,  since this latter value is necessary in order to look up any
       edge with a matching head and tail.

       Related to this, strings converted to integers act like char  pointers,
       getting  the  value  0  or  1  depending on whether the string consists
       solely of zeroes or not. Thus, the ((int)"2") evaluates to 1.

       The language inherits the usual C problems such as dangling  references
       and the confusion between '=' and '=='.

AUTHOR
       Emden R. Gansner <erg@research.att.com>


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+------------------+
       |ATTRIBUTE TYPE | ATTRIBUTE VALUE  |
       +---------------+------------------+
       |Availability   | image/graphviz   |
       +---------------+------------------+
       |Stability      | Volatile         |
       +---------------+------------------+
SEE ALSO
       awk(1), gc(1), dot(1), nop(1), expr(3), cgraph(3)



NOTES
       This     software     was    built    from    source    available    at
       https://github.com/oracle/solaris-userland.   The  original   community
       source  was  downloaded from  http://www.graphviz.org/pub/graphviz/sta-
       ble/SOURCES/graphviz-2.28.0.tar.gz

       Further information about this software can be found on the open source
       community website at http://www.graphviz.org/.



                                  3 July 2009                          GVPR(1)