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1 .TH ACYCLIC 1 "21 March 2001"
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2 .SH NAME
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3 acyclic \- make directed graph acyclic
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4 .SH SYNOPSIS
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5 .B acyclic
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6 [
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7 .B \-nv?
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8 ] [
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9 .B \-o
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10 .I outfile
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11 ]
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12 [
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13 .I file
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14 ]
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15 .SH DESCRIPTION
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16 .B acyclic
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17 is a filter that takes a directed graph as input and outputs
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18 a copy of the graph with sufficient edges reversed to make
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19 the graph acyclic. The reversed edge inherits all of the attributes
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20 of the original edge. The optional file argument specifies where the
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21 the input graph is stored; by default, the program reads from \fBstdin\fP.
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22 .SH OPTIONS
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23 The following options are supported:
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24 .TP
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25 .B \-n
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26 No output is produced, though the return value
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27 will indicate whether the graph is acyclic or not.
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28 .TP
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29 .B \-v
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30 Print information about whether the file is acyclic, has a cycle or
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31 is undirected.
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32 .TP
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33 .BI \-o " outfile"
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34 causes the output to be written to the specified file; by default,
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35 output is written to \fBstdout\fP.
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36 .TP
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37 .B \-?
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38 option causes the program to print usage information.
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39 .SH RETURN CODES
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40 .B acyclic
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41 returns
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42 .B 0
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43 if the graph is acyclic;
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44 .B 1
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45 if the graph has a cycle;
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46 .B 2
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47 if the graph is undirected; and
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48 .B 255
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49 if there are any errors.
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50 .SH BUGS
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51 If the graph is strict and there is a cycle of length 2,
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52 the attributes of the reversed edge are lost.
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53 .PP
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54 Some edge attributes are non-symmetric, referring to either the head
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55 or tail node. At present, there is no mechanism or convention for
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56 for correctly switching or renaming these.
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57 .SH AUTHORS
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58 Stephen C. North <north@research.att.com>
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59 .br
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60 Emden R. Gansner <erg@research.att.com>
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61 .SH "SEE ALSO"
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62 gc(1), dot(1), gvpr(1), gvcolor(1), ccomps(1), sccmap(1), tred(1), libgraph(3)
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