Интерактивная система просмотра системных руководств (manов)
gvpr (1)
>> gvpr (1) ( Linux man: Команды и прикладные программы пользовательского уровня )
NAME
gvpr  graph pattern scanning and processing language
( previously known as
gpr
)
SYNOPSIS
gvpr
[
icV?]
[
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
libagraph(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 predicateaction rules supplied in the input program.
The rules are evaluated in order.
For each predicate evaluating to true, the corresponding
action is performed.
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, initially 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 whitespaceseparated tokens,
with the individual tokens
available as strings in the gvpr program
as ARGV[0],...,ARGV[ARGC1].
 c

Use the source graph as the output graph.
 i

Derive the nodeinduced 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
f
is not given,
gvpr
will use the first nonoption argument as the program.
 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 predicateaction 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, BEG_G,
END_G and END clauses.
There can be any number of N and E statements,
the first applied to nodes, the second to edges.
The toplevel semantics of a gvpr program are:
Evaluate the BEGIN clause, if any.
For each input graph G {
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 predicate 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 associated node or edge is added to the target graph.
Predicates and actions are sequences of statements in the C dialect
supported by the
libexpr(3)
library.
The only difference between predicates and actions is that the former
must have a type that may interpreted as either true or false.
Here the usual C convention is followed, in which a nonzero value is
considered true. This would include nonempty strings and nonempty
references to nodes, edges, etc. However, 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 graphbased 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 '...'. In certain contexts, string values are
interpreted as patterns for the purpose of regular expression matching.
Patterns use
ksh(1)
file match pattern syntax.
gvpr uses C++ comments.
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 [ var ]
where the var is optional. As in C, variables and arrays must
be declared. In particular, an undeclared variable 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
while( expression ) statement
switch( expression ) case statements
break [ expression ]
continue [ expression ]
return [ expression ]
In the second form of the for statement, the variable var
is set to each value used as an index in the specified array and then
the associated statement is evaluated. 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.
gvpr will attempt to use an expression as a string or numeric value
as appropriate.
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 resulting 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
libagraph(3)
model, attributes are stringvalued.
In addition,
gvpr
supports certain pseudoattributes of graph objects, not necessarily
stringvalued. 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 "<tailname><edgeop><headname>[<key>]",
where <edgeop> is ">" or "" depending on
whether the graph is directed or not. The bracket part [<key>]
only appears if the edge has a nontrivial 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 (nonzero) if the graph is directed
 strict : int

true (nonzero) if the graph is strict
BUILTIN 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 nonstrict, respectively. If t is empty,
a directed, nonstrict 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, or NULL.
 isNode(sg : graph_t, s : string) : node_t

looks for a node in graph g of name s. If such a node
exists, it is returned. Otherwise, NULL is returned.
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. If the graph is undirected, the distinction between
head and tail nodes is unimportant.
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.
 fstout(n : node_t) : edge_t

returns the first out edge of node n.
 nxtout(e : edge_t) : edge_t

returns the next out edge after e.
 fstin(n : node_t) : edge_t

returns the first in edge of node n.
 nxtin(e : edge_t) : edge_t

returns the next in edge after e.
 fstedge(n : node_t) : edge_t

returns the first edge of node n.
 nxtedge(e : edge_t) : edge_t

returns the next edge after e.
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 integer 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.
If x is a graph, this indicates that g is the immediate parent
graph of x.
 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 implicitly cloned.
If a graph is cloned, all nodes, edges and subgraphs are implicitly
cloned.
If x is a graph, g may be NULL, in which case the cloned
object will be a new root graph.
 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.
 induce(g : graph_t) : void

extends g to its nodeinduced subgraph extension in its root graph.
 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.
 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)
format
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.
 length(s : string) : int

returns the length of the string s.
 index(s : string, t : string) : int

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

returns a version of s appropriate to be used as an identifier
in a dot file.
 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.
I/O
 print(...) : void

print( expr, ... )
prints a string representation of each argument 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.
 openF(s : string, t : string) : int

opens the file s as an I/O stream. The string argument t
specifies 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 character 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.
Miscellaneous
 exit() : void

 exit(v : int) : void

causes
gvpr
to exit with the exit code
v.
v
defaults to 0 if omitted.
 rand() : double

returns a pseudorandom double between 0 and 1.
 srand() : int

 srand(v : int) : int

sets a seed for the random number generator. The optional argument 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.
BUILTIN VARIABLES
gvpr
provides certain special, builtin 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 initialized
to the target graph. After traversal and any END_G actions,
if it refers to a nonempty 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)
depthfirst traversal of the
graph (cf. $tvtype below).
The default value is NULL for each input graph.
 $tvtype : tvtype_t

indicates how gvpr traverses a graph. At present, it can only take
one of six values: TV_flat, TV_dfs, TV_fwd,
TV_ref, TV_ne, and TV_en. TV_flat is the default.
The meaning of these values is discussed below.
 ARGC : int

denotes the number of arguments specified by the
a args commandline argument.
 ARGV : string array

denotes the array of arguments specified by the
a args
commandline argument. The ith argument is given
by ARGV[i].
BUILTIN 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
seemingly 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

a traversal of the graph using a depthfirst 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 traversal will stop. Note that using
TV_dfs and $tvroot, it is possible to create an infinite loop.
 TV_fwd : tvtype_t

a traversal of the graph using a depthfirst search on the
graph following only forward arcs. In
libagraph(3),
edges in undirected graphs are given an arbitrary direction, which is
used for this traversal. The choice of roots for the traversal is the
same as described for TV_dfs above.
 TV_rev : tvtype_t

a traversal of the graph using a depthfirst search on the
graph following only reverse arcs. In
libagraph(3),
edges in undirected graphs are given an arbitrary direction, which is
used for this traversal. The choice of roots for the traversal is the
same as described for TV_dfs above.
EXAMPLES
gvpr i 'N[color=="blue"]' file.dot
Generate the nodeinduced subgraph of all nodes with color blue.
gvpr c 'N[color=="blue"]{color = "red"}' file.dot
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 %s, n, e, $G.name);
tot_n += n;
tot_e += e;
}
END { printf ("%d nodes %d edges total, tot_n, tot_e) }
Version of the program
gc.
gvpr c ""
Equivalent to
nop.
BEG_G { graph_t g = graph ("merge", "S"); }
E {
node_t h = clone(g,$.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] = %d, n.name, deg[n]);
}
}
Computes the degrees of nodes with edges.
BUGS
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.
The constants TV_flat, TV_dfs, TV_fwd, and TV_rev
There is a single scope and the extent of all variables is
the entire life of the program. It might be preferable for scope
to reflect the natural nesting of the clauses, or for the program
to at least reset locally declared variables.
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.
The language inherits the usual C problems such as dangling references
and the confusion between '=' and '=='.
AUTHOR
Emden R. Gansner <
erg@research.att.com>
SEE ALSO
awk(1), gc(1), dot(1), nop(1), libexpr(3), libagraph(3)
Index
 NAME

 SYNOPSIS

 DESCRIPTION

 OPTIONS

 OPERANDS

 PROGRAMS

 BUILTIN FUNCTIONS

 Graphs and subgraph

 Nodes

 Edges

 Graph I/O

 Graph miscellany

 Strings

 I/O

 Math

 Miscellaneous

 BUILTIN VARIABLES

 BUILTIN CONSTANTS

 EXAMPLES

 BUGS

 AUTHOR

 SEE ALSO
