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first hg version after svn

.TH DOT 1 "23 August 2004" \*(eX
.SH NAME
dot \- filter for drawing directed graphs
.br
neato \- filter for drawing undirected graphs
.br
twopi \- filter for radial layouts of graphs
.br
circo \- filter for circular layout of graphs
.br
fdp \- filter for drawing undirected graphs
.br
sfdp \- filter for drawing large undirected graphs
.SH SYNOPSIS
\fBdot\fR
[\fB\-\fR(\fBG\fR|\fBN\fR|\fBE\fR)\fIname=value\fR]
[\fB\-T\fIlang\fR]
[\fB\-l\fIlibfile\fR]
[\fB\-o\fIoutfile\fR]
[\fB\-K\fIlayout\fR]
[\fB\-O\fR]
[\fB\-P\fR]
[\fB\-v\fR]
[\fB\-V\fR]
[files]
.br
\fBneato\fR
[\fB\-\fR(\fBG\fR|\fBN\fR|\fBE\fR)\fIname=value\fR]
[\fB\-T\fIlang\fR]
[\fB\-l\fIlibfile\fR]
[\fB\-n\fR[\fB1\fR|\fB2\fR]]
[\fB\-o\fIoutfile\fR]
[\fB\-K\fIlayout\fR]
[\fB\-O\fR]
[\fB\-P\fR]
[\fB\-v\fR]
[\fB\-V\fR]
[files]
.br
\fBtwopi\fR
[\fB\-\fR(\fBG\fR|\fBN\fR|\fBE\fR)\fIname=value\fR]
[\fB\-T\fIlang\fR]
[\fB\-l\fIlibfile\fR]
[\fB\-o\fIoutfile\fR]
[\fB\-K\fIlayout\fR]
[\fB\-O\fR]
[\fB\-P\fR]
[\fB\-v\fR]
[\fB\-V\fR]
[files]
.br
\fBcirco\fR
[\fB\-\fR(\fBG\fR|\fBN\fR|\fBE\fR)\fIname=value\fR]
[\fB\-T\fIlang\fR]
[\fB\-l\fIlibfile\fR]
[\fB\-o\fIoutfile\fR]
[\fB\-K\fIlayout\fR]
[\fB\-O\fR]
[\fB\-P\fR]
[\fB\-v\fR]
[\fB\-V\fR]
[files]
.br
\fBfdp\fR
[\fB\-\fR(\fBG\fR|\fBN\fR|\fBE\fR)\fIname=value\fR]
[\fB\-T\fIlang\fR]
[\fB\-l\fIlibfile\fR]
[\fB\-o\fIoutfile\fR]
[\fB\-K\fIlayout\fR]
[\fB\-O\fR]
[\fB\-P\fR]
[\fB\-v\fR]
[\fB\-V\fR]
[files]
.br
\fBsfdp\fR
[\fB\-\fR(\fBG\fR|\fBN\fR|\fBE\fR)\fIname=value\fR]
[\fB\-T\fIlang\fR]
[\fB\-l\fIlibfile\fR]
[\fB\-o\fIoutfile\fR]
[\fB\-K\fIlayout\fR]
[\fB\-O\fR]
[\fB\-P\fR]
[\fB\-v\fR]
[\fB\-V\fR]
[files]
.SH DESCRIPTION
.I dot
draws directed graphs.  It works well on DAGs and other graphs
that can be drawn as hierarchies.
It reads attributed graph files and writes drawings.
By default, the output format
.I dot
is the input file with layout coordinates appended.
.PP
.I neato
draws undirected graphs using ``spring'' models (see Kamada and Kawai,
Information Processing Letters 31:1, April 1989).  Input files must be
formatted in the
.I dot
attributed graph language.
By default, the output of
.I neato
is the input graph with layout coordinates appended.
.PP
.I twopi
draws graphs using a radial layout (see G. Wills,
Symposium on Graph Drawing GD'97, September, 1997).
Basically, one node is chosen as the center and put at the origin.
The remaining nodes are placed on a sequence of concentric circles
centered about the origin, each a fixed radial distance from the
previous circle.
All nodes distance 1 from the center are placed on the first circle;
all nodes distance 1 from a node on the first circle are placed on
the second circle; and so forth.
.PP
.I circo
draws graphs using a circular layout (see
Six and Tollis, GD '99 and ALENEX '99, and
Kaufmann and Wiese, GD '02.)
The tool identifies biconnected components and draws the nodes of
the component on a circle. The block\(hycutpoint tree
is then laid out using a recursive radial algorithm. Edge
crossings within a circle are minimized by placing as many edges on
the circle's perimeter as possible.
In particular, if the component is outerplanar, the component will
have a planar layout.
.PP
If a node belongs to multiple non\(hytrivial biconnected components,
the layout puts the node in one of them. By default, this is the first
non\(hytrivial component found in the search from the root component.
.PP
.I fdp
draws undirected graphs using a ``spring'' model. It relies on a
force\(hydirected approach in the spirit of Fruchterman and Reingold
(cf. Software\(hyPractice & Experience 21(11), 1991, pp. 1129\(hy1164).
.PP
.I sfdp
also draws undirected graphs using the ``spring'' model described
above, but it uses a multi-scale approach to produce layouts
of large graphs in a reasonably short time.
.SH OUTPUT FORMATS
Dot uses an extensible plugin mechanism for its output renderers,
so to see what output formats your installation of dot supports
you can use ``dot \-Txxx'' (where xxx is an unlikely format)
and check the warning message.
Also, The plugin mechanism supports multiple implementations
of the output formats.
To see what variants are available, use, for example: ``dot \-Tpng:''
and to force a particular variant, use, for example: ``dot \-Tpng:gd''
.P
Traditionally, dot supports the following:
\fB\-Tps\fP (PostScript),
\fB\-Tsvg\fP \fB\-Tsvgz\fP (Structured Vector Graphics),
\fB\-Tfig\fP (XFIG graphics),
\fB\-Tmif\fP (FrameMaker graphics),
\fB\-Thpgl\fP (HP pen plotters), and \fB\-Tpcl\fP (Laserjet printers),
\fB\-Tpng\fP \fB\-Tgif\fP (bitmap graphics),
\fB\-Tdia\fP (GTK+ based diagrams),
\fB\-Timap\fP (imagemap files for httpd servers for each node or edge
that has a non\(hynull "href" attribute.),
\fB\-Tcmapx\fP (client\(hyside imagemap for use in html and xhtml).
Additional less common or more special\(hypurpose output formats
can be found at http://www.graphviz.org/cvs/doc/info/output.html.)
.P
Alternative plugins providing support for a given output format
can be found from the error message resulting from appending a ':' to the format. e.g. \fB-Tpng:\fP
The first plugin listed is always the default.
.P
The \fB\-P\fP switch can be used to produce a graph of all output variants supported by plugins in the local installation of graphviz.
.SH GRAPH FILE LANGUAGE
Here is a synopsis of the graph file language, traditionally using the extension \fB.dot\fR, for graphs:
.PP
[\fBstrict\fR] (\fBgraph\fR|\fBdigraph\fR) \fIname\fP { \fIstatement\(hylist\fP }\fR
.br 
Is the top level graph. If the graph is \fBstrict\fR then multiple edges are
not allowed between the same pairs of nodes.
If it is a directed graph, indicated by \fBdigraph\fR,
then the \fIedgeop\fR must be "\->". If it is an undirected \fBgraph\fR
then the \fIedgeop\fR must be "\-\-".
Statements may be:
.PP
\fIname\fB=\fIval\fB;\fR
.br
\fBnode [\fIname\fB=\fIval\fB];\fR
.br
\fBedge [\fIname\fB=\fIval\fB];\fR
.br
Set default graph, node, or edge attribute \fIname\fP to \fIval\fP.
Any subgraph, node, or edge appearing after this inherits the new
default attributes.
.PP
\fBn0 [\fIname0=val0,name1=val1,...\fB];\fR
Creates node \fBn0\fP (if it does not already exist)
and sets its attributes according to the optional list. 
.PP
\fBn0 \fIedgeop\fR n1 \fIedgeop\fR \fI...\fB \fIedgeop\fR nn [\fIname0=val0,name1=val1,...\fB];\fR
.br
Creates edges between nodes \fBn0\fP, \fBn1\fP, ..., \fBnn\fP and sets
their attributes according to the optional list.
Creates nodes as necessary.
.PP
[\fBsubgraph \fIname\fB] { \fIstatement\(hylist \fB}\fR
.br
Creates a subgraph.  Subgraphs may be used in place
of \fBn0\fP, ..., \fBnn\fP in the above statements to create edges.
[\fBsubgraph \fIname\fR] is optional;
if missing, the subgraph is assigned an internal name. 
.PP
Comments may be /*C\(hylike*/ or //C++\(hylike.

.PP
Attribute names and values are ordinary (C\(hystyle) strings.
The following sections describe attributes that control graph layout.

.SH "GRAPH ATTRIBUTES"
.PP
\fBsize="\fIx,y\fP"\fR sets bounding box of drawing in inches.
.PP
\fBpage="\fIx,y\fP"\fR sets the PostScript pagination unit.
.PP
\fBratio=\fIf\fR sets the aspect ratio to \fIf\fP which may be
a floating point number, or one of the keywords \fBfill\fP,
\fBcompress\fP, or \fBauto\fP.
.PP
\fBlayout=\fIengine\fR indicates the preferred layout engine ("dot", "neato", fdp" etc) overriding the default from the basename of the command or the -K commandline option.
.PP
\fBmargin=\fIf\fR sets the page margin (included in the page size).
.PP
\fBnodesep=\fIf\fR sets the minimum separation between nodes.
.PP
\fBranksep=\fIf\fR sets the minimum separation between ranks.
.PP
\fBordering=out\fR constrains order of out\(hyedges in a subgraph
according to their file sequence.
.PP
\fBrankdir=LR|RL|BT\fR requests a left\(hyto\(hyright, right\(hyto\(hyleft, or bottom\(hyto\(hytop, drawing.
.PP
\fBpagedir=\fR[TBLR][TBLR] sets the major and minor order of pagination.
.PP
\fBrank=same\fR (or \fBmin\fP or \fBmax\fP) in a subgraph
constrains the rank assignment of its nodes.   If a subgraph's
name has the prefix \fBcluster\fP, its nodes are drawn in
a distinct rectangle of the layout.  Clusters may be nested.
.PP
\fBrotate=90\fR sets landscape mode. 
(\fBorientation=land\fR is backward compatible but obsolete.)
.PP
\fBcenter=\fIn\fR a non\(hyzero value centers the drawing on the page.
.PP
\fBnslimit=\fIf\fR or \fBmclimit=\fIf\fR adjusts the bound on the
number of network simplex or mincross iterations by the given ratio.
For example, \fBmclimit=2.0\fP runs twice as long.
.PP
\fBlayers="\fIid:id:id:id\fR" is a sequence of layer identifiers for
overlay diagrams.  The PostScript array variable \fIlayercolorseq\fR
sets the assignment of colors to layers. The least index is 1 and 
each element must be a 3\(hyelement array to be interpreted as a color coordinate.
.PP
\fBcolor=\fIcolorvalue\fR sets foreground color (\fBbgcolor\fP for background).
.PP
\fBhref=\fI"url"\fR the default url for image map files; in PostScript files,
the base URL for all relative URLs, as recognized by Acrobat Distiller
3.0 and up.
.PP
\fBURL=\fI"url"\fR ("URL" is a synonym for "href".)
.PP
\fBstylesheet=\fI"file.css"\fR includes a reference to a stylesheet
in \-Tsvg and \-Tsvgz outputs.  Ignored by other formats.
.PP
\fBsplines\fR. If set to \fItrue\fR, edges are
drawn as splines.
If set to \fIpolyline\fR, edges are 
drawn as polylines.
If set to \fIortho\fR, edges are 
drawn as orthogonal polylines.
In all of these cases, the nodes may not overlap.
If \fBsplines=\fIfalse\fR or \fBsplines=\fIline\fR, edges are 
drawn as line segments.
The default is \fItrue\fR for dot, and \fIfalse\fR for all other layouts.

.PP
\fB(neato\(hyspecific attributes)\fR
.br
\fBstart=\fIval\fR.  Requests random initial placement and seeds
the random number generator.  If \fIval\fP is not an integer,
the process ID or current time is used as the seed.
.PP
\fBepsilon=\fIn\fR.  Sets the cutoff for the solver.
The default is 0.1.

.PP
\fB(twopi\(hyspecific attributes)\fR
.br
\fBroot=\fIctr\fR. This specifies the node to be used as the center of
the layout. If not specified, \fItwopi\fP will randomly pick one of the
nodes that are furthest from a leaf node, where a leaf node is a node
of degree 1. If no leaf nodes exists, an arbitrary node is picked as center.
.PP
\fBranksep=\fIval\fR. Specifies the radial distance in inches between
the sequence of rings. The default is 0.75.
.PP
\fBoverlap=\fImode\fR. This specifies what \fItwopi\fP should do if
any nodes overlap. If mode is \fI"false"\fP, the program uses Voronoi
diagrams to adjust the nodes to eliminate overlaps. If mode is \fI"scale"\fP,
the layout is uniformly scaled up, preserving node sizes, until nodes no
longer overlap. The latter technique removes overlaps while preserving
symmetry and structure, while the former removes overlaps more compactly
but destroys symmetries.
If mode is \fI"true"\fP (the default), no repositioning is done.

.PP
\fB(circo\(hyspecific attributes)\fR
.br
\fBroot=\fInodename\fR. Specifies the name of a node occurring in the
root block. If the graph is disconnected, the \fBroot\fP node attribute
can be used to specify additional root blocks.
.PP
\fBmindist=\fIvalue\fR. Sets the minimum separation between all nodes. If not
specified then \fIcirco\fP uses a default value of 1.0.

.PP
\fB(fdp\(hyspecific attributes)\fR
.br
\fBK=\fIval\fR. Sets the default ideal node separation
in the layout.
.PP
\fBmaxiter=\fIval\fR. Sets the maximum number of iterations used to
layout the graph.
.PP
\fBstart=\fIval\fR. Adjusts the random initial placement of nodes
with no specified position.  If \fIval\fP is is an integer,
it is used as the seed for the random number generator.
If \fIval\fP is not an integer, a random system\(hygenerated integer,
such as the process ID or current time, is used as the seed.
.PP

.SH "NODE ATTRIBUTES"
.PP
\fBheight=\fId\fR or \fBwidth=\fId\fR sets minimum height or width.
Adding \fBfixedsize=true\fP forces these to be the actual size
(text labels are ignored).
.PP
\fBshape=record polygon epsf \fIbuiltin_polygon\fR
.br
\fIbuiltin_polygon\fR is one of: \fBplaintext ellipse oval circle egg 
triangle box diamond trapezium parallelogram house hexagon octagon
note tab box3d component.\fR
(Polygons are defined or modified by the following node attributes:
\fBregular\fR, \fBperipheries\fR, \fBsides\fR, \fBorientation\fR,
\fBdistortion\fR and \fBskew\fR.)  \fBepsf\fR uses the node's
\fBshapefile\fR attribute as the path name of an external
EPSF file to be automatically loaded for the node shape.
.PP
\fBlabel=\fItext\fR where \fItext\fP may include escaped newlines
\\\|n, \\\|l, or \\\|r for center, left, and right justified lines.
The string '\\N' value will be replaced by the node name.
The string '\\G' value will be replaced by the graph name.
Record labels may contain recursive box lists delimited by { | }.
Port identifiers in labels are set off by angle brackets < >.
In the graph file, use colon (such as, \fBnode0:port28\fR).
.PP
\fBfontsize=\fIn\fR sets the label type size to \fIn\fP points.
.PP
\fBfontname=\fIname\fR sets the label font family name.
.PP
\fBcolor=\fIcolorvalue\fR sets the outline color, and the default fill color
if style=filled and \fBfillcolor\fR is not specified.
.PP
\fBfillcolor=\fIcolorvalue\fR sets the fill color
when style=filled.  If not specified, the fillcolor when style=filled defaults
to be the same as the outline color.
.PP
\fBfontcolor=\fIcolorvalue\fR sets the label text color.
.PP
A \fIcolorvalue\fP may be "\fIh,s,v\fB"\fR (hue, saturation, brightness)
floating point numbers between 0 and 1, or an X11 color name such as
\fBwhite black red green blue yellow magenta cyan\fR or \fBburlywood\fR,
or a "\fI#rrggbb" (red, green, blue, 2 hex characters each) value.
.PP
\fBstyle=filled solid dashed dotted bold invis\fP or any Postscript code.
.PP
\fBlayer=\fIid\fR or \fIid:id\fR or "all" sets the node's active layers.
The empty string means no layers (invisible).
.PP
The following attributes apply only to polygon shape nodes:
.PP
\fBregular=\fIn\fR if \fIn\fR is non\(hyzero then the polygon is made 
regular, i.e. symmetric about the x and y axis, otherwise the
polygon takes on the aspect ratio of the label. 
\fIbuiltin_polygons\fR that are not already regular are made regular
by this attribute.
\fIbuiltin_polygons\fR that are already regular are not affected (i.e.
they cannot be made asymmetric).
.PP
\fBperipheries=\fIn\fR sets the number of periphery lines drawn around
the polygon.  This value supersedes the number of periphery lines
of \fIbuiltin_polygons\fR.
.PP
\fBsides=\fIn\fR sets the number of sides to the polygon. \fIn\fR<3
results in an ellipse.
This attribute is ignored by \fIbuiltin_polygons\fR.
.PP
\fBorientation=\fIf\fR sets the orientation of the first apex of the
polygon counterclockwise from the vertical, in degrees.
\fIf\fR may be a floating point number.
The orientation of labels is not affected by this attribute.
This attribute is added to the initial orientation of \fIbuiltin_polygons.\fR
.PP
\fBdistortion=\fIf\fR sets the amount of broadening of the top and
narrowing of the bottom of the polygon (relative to its orientation). 
Floating point values between \-1 and +1 are suggested.
This attribute is ignored by \fIbuiltin_polygons\fR.
.PP                                                            
\fBskew=\fIf\fR sets the amount of right\(hydisplacement of the top and
left\(hydisplacement of the bottom of the polygon (relative to its
orientation).
Floating point values between \-1 and +1 are suggested.
This attribute is ignored by \fIbuiltin_polygons\fR.
.PP
\fBhref=\fI"url"\fR sets the url for the node in imagemap, PostScript and SVG
files.
The substrings '\\N' and '\\G' are substituted in the same manner as
for the node label attribute.
Additionally the substring '\\L' is substituted with the node label string.
.PP
\fBURL=\fI"url"\fR ("URL" is a synonym for "href".)
.PP
\fBtarget=\fI"target"\fR is a target string for client\(hyside imagemaps
and SVG, effective when nodes have a URL.
The target string is used to determine which window of the browser is used
for the URL.  Setting it to "_graphviz" will open a new window if it doesn't
already exist, or reuse it if it does.
If the target string is empty, the default,
then no target attribute is included in the output.
The substrings '\\N' and '\\G' are substituted in the same manner as
for the node label attribute.
Additionally the substring '\\L' is substituted with the node label string.
.PP
\fBtooltip=\fI"tooltip"\fR is a tooltip string for client\(hyside imagemaps
and SVG, effective when nodes have a URL.  The tooltip string defaults to be the
same as the label string, but this attribute permits nodes without
labels to still have tooltips thus permitting denser graphs.
The substrings '\\N' and '\\G' are substituted in the same manner as
for the node label attribute.
Additionally the substring '\\L' is substituted with the node label string.

.PP
\fB(circo\(hyspecific attributes)\fR
.br
\fBroot=\fItrue/false\fR. This specifies that the block containing the given
node be treated as the root of the spanning tree in the layout.

.PP
\fB(fdp\(hyspecific attributes)\fR
.br
\fBpin=\fIval\fR. If \fIval\fR is "true", the node will remain at
its initial position.

.SH "EDGE ATTRIBUTES"
\fBminlen=\fIn\fR where \fIn\fP is an integer factor that applies
to the edge length (ranks for normal edges, or minimum node separation
for flat edges).
.PP
\fBweight=\fIn\fR where \fIn\fP is the integer cost of the edge.
Values greater than 1 tend to shorten the edge.  Weight 0 flat
edges are ignored for ordering nodes.
.PP
\fBlabel=\fItext\fR where \fItext\fR may include escaped newlines
\\\|n, \\\|l, or \\\|r for centered, left, or right justified lines.
If the substring '\\T' is found in a label it will be replaced by the tail_node name.
If the substring '\\H' is found in a label it will be replaced by the head_node name.
If the substring '\\E' value is found in a label it will be replaced by: tail_node_name\->head_node_name
If the substring '\\G' is found in a label it will be replaced by the graph name.
or by: tail_node_name\-\-head_node_name for undirected graphs.
.PP
\fBfontsize=\fIn\fR sets the label type size to \fIn\fP points.
.PP
\fBfontname=\fIname\fR sets the label font family name.
.PP
\fBfontcolor=\fIcolorvalue\fR sets the label text color.
.PP
\fBstyle=solid dashed dotted bold invis\fP
.PP
\fBcolor=\fIcolorvalue\fR sets the line color for edges.
.PP
\fBcolor=\fIcolorvaluelist\fR a ':' separated list of \fIcolorvalue\fR creates
parallel edges, one edge for each color.
.PP
\fBdir=forward back both none\fP controls arrow direction.
.PP
\fBtailclip,headclip=false\fP disables endpoint shape clipping.
.PP
\fBhref=\fI"url"\fR sets the url for the node in imagemap, PostScript and SVG
files.
The substrings '\\T', '\\H', '\\E' and '\\G' are substituted in the same manner as
for the edge label attribute.
Additionally the substring '\\L' is substituted with the edge label string.
.PP
\fBURL=\fI"url"\fR ("URL" is a synonym for "href".)
.PP
\fBtarget=\fI"target"\fR is a target string for client\(hyside imagemaps
and SVG, effective when edges have a URL.
If the target string is empty, the default,
then no target attribute is included in the output.
The substrings '\\T', '\\H', '\\E' and '\\G' are substituted in the same manner as
for the edge label attribute.
Additionally the substring '\\L' is substituted with the edge label string.
.PP
\fBtooltip=\fI"tooltip"\fR is a tooltip string for client\(hyside imagemaps
effective when edges have a URL.  The tooltip string defaults to be the
same as the edge label string. 
The substrings '\\T', '\\H', '\\E' and '\\G' are substituted in the same manner as
for the edge label attribute.
Additionally the substring '\\L' is substituted with the edge label string.
.PP
\fBarrowhead,arrowtail=none, normal, inv, dot, odot, invdot, invodot,
tee, empty, invempty, open, halfopen, diamond, odiamond, box, obox, crow\fP.
.PP
\fBarrowsize\fP (norm_length=10,norm_width=5,
inv_length=6,inv_width=7,dot_radius=2) 
.PP
\fBheadlabel,taillabel=string\fP for port labels.
\fBlabelfontcolor\fP,\fBlabelfontname\fP,\fBlabelfontsize\fP
for head and tail labels.
The substrings '\\T', '\\H', '\\E' and '\\G' are substituted in the same manner as
for the edge label attribute.
Additionally the substring '\\L' is substituted with the edge label string.
.PP
\fBheadhref=\fI"url"\fR sets the url for the head port in imagemap, PostScript and SVG files.
The substrings '\\T', '\\H', '\\E' and '\\G' are substituted in the same manner as
for the edge label attribute.
Additionally the substring '\\L' is substituted with the edge label string.
.PP
\fBheadURL=\fI"url"\fR ("headURL" is a synonym for "headhref".)
.PP
\fBheadtarget=\fI"headtarget"\fR is a target string for client\(hyside imagemaps
and SVG, effective when edge heads have a URL.
The headtarget string is used to determine which window of the browser is used
for the URL.  If the headtarget string is empty, the default,
then headtarget defaults to the same value as target for the edge.
The substrings '\\T', '\\H', '\\E' and '\\G' are substituted in the same manner as
for the edge label attribute.
Additionally the substring '\\L' is substituted with the edge label string.
.PP
\fBheadtooltip=\fI"tooltip"\fR is a tooltip string for client\(hyside imagemaps
effective when head ports have a URL.  The tooltip string defaults to be the
same as the headlabel string. 
The substrings '\\T', '\\H', and '\\E' are substituted in the same manner as
for the edge label attribute.
Additionally the substring '\\L' is substituted with the edge label string.
.PP
\fBtailhref=\fI"url"\fR sets the url for the tail port in imagemap, PostScript and SVG files.
The substrings '\\T', '\\H', '\\E' and '\\G' are substituted in the same manner as
for the edge label attribute.
Additionally the substring '\\L' is substituted with the edge label string.
.PP
\fBtailURL=\fI"url"\fR ("tailURL" is a synonym for "tailhref".)
.PP
\fBtailtarget=\fI"tailtarget"\fR is a target string for client\(hyside imagemaps
and SVG, effective when edge tails have a URL.
The tailtarget string is used to determine which window of the browser is used
for the URL.  If the tailtarget string is empty, the default,
then tailtarget defaults to the same value as target for the edge.
The substrings '\\T', '\\H', '\\E' and '\\G' are substituted in the same manner as
for the edge label attribute.
Additionally the substring '\\L' is substituted with the edge label string.
.PP
\fBtailtooltip=\fI"tooltip"\fR is a tooltip string for client\(hyside imagemaps
effective when tail ports have a URL.  The tooltip string defaults to be the
same as the taillabel string. 
The substrings '\\T', '\\H', '\\E' and '\\G' are substituted in the same manner as
for the edge label attribute.
Additionally the substring '\\L' is substituted with the edge label string.
.PP
\fBlabeldistance\fP and \fPport_label_distance\fP set distance; also
\fBlabelangle\fP (in degrees CCW)
.PP
\fBdecorate\fP draws line from edge to label.
.PP
\fBsamehead,sametail\fP aim edges having the same value to the
same port, using the average landing point.
.PP
\fBconstraint=false\fP causes an edge to be ignored for rank assignment.
.PP
\fBlayer=\fIid\fR or \fIid:id\fR or "all" sets the edge's active layers.
The empty string means no layers (invisible).

.PP
\fB(neato\(hyspecific attributes)\fR
.br
\fBw=\fIf\fR sets the weight (spring constant) of an edge
to the given floating point value.  The default is 1.0;
greater values make the edge tend more toward its optimal length.
.PP
\fBlen=\fIf\fR sets the optimal length of an edge.
The default is 1.0.
.PP
\fB(fdp\(hyspecific attributes)\fR
.br
\fBweight=\fIf\fR sets the weight of an edge
to the given floating point value. The default is 1.0;
greater values make the edge tend more toward its optimal length.
.SH "COMMAND LINE OPTIONS"
\fB\-G\fP sets a default graph attribute.
.br
\fB\-N\fP sets a default node attribute.
.br
\fB\-E\fP sets a default edge attribute.
Example: \fB\-Gsize="7,8" \-Nshape=box \-Efontsize=8\fR
.PP
\fB\-l\fIfile\fR loads custom PostScript library files.
Usually these define custom shapes or styles.
If \fB\-l\fP is given by itself, the standard library is omitted.
.PP
\fB\-T\fIlang\fR sets the output language as described above.

.PP
\fB\-n\fR[\fB1\fR|\fB2\fR] (no\(hyop)
If set, neato assumes nodes have already been positioned and all
nodes have a pos attribute giving the positions.
It then performs an optional adjustment to remove node\(hynode overlap,
depending on the value of the overlap attribute,
computes the edge layouts, depending on the value of the \fBsplines\fR attribute,
and emits the graph in the appropriate format.
If num is supplied, the following actions occur:
.nf
    num = 1
.fi
Equivalent to \-n.
.nf
    num > 1
.fi
Use node positions as specified,
with no adjustment to remove node\(hynode overlaps,
and use any edge layouts already specified by the pos attribute.
neato computes an edge layout for any edge that does not have a pos attribute.
As usual, edge layout is guided by the \fBsplines\fR attribute.
.PP
\fB\-K\fIlayout\fR override the default layout engine implied by the command name.
.PP
\fB\-O\fP automatically generate output filenames based on the input filename and the -T format.
.PP
\fB\-P\fP generate a graph of the currently available plugins.
.PP
\fB\-v\fP (verbose) prints various information useful for debugging.
.PP
\fB\-V\fP (version) prints version information and exits.
.PP
\fB\-?\fP prints the usage and exits.
.SH "EXAMPLES"
.nf
digraph test123 {
        a \-> b \-> c;
        a \-> {x y};
        b [shape=box];
        c [label="hello\\\|nworld",color=blue,fontsize=24,
             fontname="Palatino\-Italic",fontcolor=red,style=filled];
        a \-> z [label="hi", weight=100];
        x \-> z [label="multi\-line\\\|nlabel"];
        edge [style=dashed,color=red];
        b \-> x;
        {rank=same; b x}
}
.fi
.PP
.nf
graph test123 {
        a \-\- b \-\- c;
        a \-\- {x y};
        x \-\- c [w=10.0];
        x \-\- y [w=5.0,len=3];
}
.fi
.SH "CAVEATS"
Edge splines can overlap unintentionally.
.PP
Flat edge labels are slightly broken.
Intercluster edge labels are totally broken.
.PP
Because unconstrained optimization is employed, node boxes can
possibly overlap or touch unrelated edges.  All existing
spring embedders seem to have this limitation.
.PP
Apparently reasonable attempts to pin nodes or adjust edge lengths
and weights can cause instability.
.SH AUTHORS
Stephen C. North <[e-mail]>
.br
Emden R. Gansner <[e-mail]>
.br
John C. Ellson <[e-mail]>
.PP
The bitmap driver (PNG, GIF etc) is by Thomas Boutell, <http://www.boutell.com/gd>
.PP
The Truetype font renderer is from
the Freetype Project (David Turner, Robert Wilhelm, and Werner Lemberg)
(who can be contacted at freetype\[e-mail]\-muenchen.de).
.SH "SEE ALSO"
This man page contains only a small amount of the information related
to the Graphviz layout programs. The most complete information can be
found at http://www.graphviz.org/Documentation.php, especially in the
on\(hyline reference pages. Most of these documents are also available in the
\fIdoc\fP and \fIdoc/info\fP subtrees in the source and binary distributions.
.PP
dotty(1)
.br
tcldot(n)
.br
xcolors(1)
.br
libgraph(3)
.PP
E. R. Gansner, S. C. North,  K. P. Vo, "DAG \(hy A Program to Draw Directed Graphs", Software \(hy Practice and Experience 17(1), 1988, pp. 1047\(hy1062.
.br
E. R. Gansner, E. Koutsofios, S. C. North,  K. P. Vo, "A Technique for Drawing Directed Graphs," IEEE Trans. on Soft. Eng. 19(3), 1993, pp. 214\(hy230.
.br
S. North and E. Koutsofios, "Applications of graph visualization",
Graphics Interface 94, pp. 234\(hy245.
.br
E. Koutsofios and S. C. North, "Drawing Graphs with dot," 
Available on research.att.com in dist/drawdag/dotguide.ps.Z.
.br
S. C. North, "NEATO User's Manual".
Available on research.att.com in dist/drawdag/neatodoc.ps.Z.