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Common output options for automata

Table of Contents

Spot supports different output syntaxes for automata. This page documents the options, common to all tools where it makes sense, that are used to specify how to output of automata.

Common output options

All tools that can output automata implement the following options:

-8, --utf8                 enable UTF-8 characters in output (ignored with
                           --lbtt or --spin)
    --check[=PROP]         test for the additional property PROP and output
                           the result in the HOA format (implies -H).  PROP
                           may be any prefix of 'all' (default),
                           'unambiguous', 'stutter-invariant', or
                           'strength'.
-d, --dot[=1|a|A|b|B|c|C(COLOR)|e|f(FONT)|h|k|K|n|N|o|r|R|s|t|u|v|y|+INT|<INT|#]                                                          GraphViz's format.
                           Add letters for (1) force numbered states, (a)
                           show acceptance condition (default), (A) hide
                           acceptance condition, (b) acceptance sets as
                           bullets, (B) bullets except for Büchi/co-Büchi
                           automata, (c) force circular nodes, (C) color
                           nodes with COLOR, (d) show origins when known, (e)
                           force elliptic nodes, (f(FONT)) use FONT, (h)
                           horizontal layout, (k) use state labels when
                           possible, (K) use transition labels (default), (n)
                           show name, (N) hide name, (o) ordered transitions,
                           (r) rainbow colors for acceptance sets, (R) color
                           acceptance sets by Inf/Fin, (s) with SCCs, (t)
                           force transition-based acceptance, (u) hide true
                           states, (v) vertical layout, (y) split universal
                           edges by color, (+INT) add INT to all set numbers,
                           (<INT) display at most INT states, (#) show
                           internal edge numbers
-H, --hoaf[=1.1|i|k|l|m|s|t|v]   Output the automaton in HOA format
                           (default).  Add letters to select (1.1) version
                           1.1 of the format, (i) use implicit labels for
                           complete deterministic automata, (s) prefer
                           state-based acceptance when possible [default],
                           (t) force transition-based acceptance, (m) mix
                           state and transition-based acceptance, (k) use
                           state labels when possible, (l) single-line
                           output, (v) verbose properties
    --lbtt[=t]             LBTT's format (add =t to force transition-based
                           acceptance even on Büchi automata)
    --name=FORMAT          set the name of the output automaton
-o, --output=FORMAT        send output to a file named FORMAT instead of
                           standard output.  The first automaton sent to a
                           file truncates it unless FORMAT starts with '>>'.
-q, --quiet                suppress all normal output
-s, --spin[=6|c]           Spin neverclaim (implies --ba).  Add letters to
                           select (6) Spin's 6.2.4 style, (c) comments on
                           states
    --stats=FORMAT, --format=FORMAT
                           output statistics about the automaton

The main three output formats (that can also been used as input to some of the tools) are HOA (used by default, or with -H or --hoaf), LBTT (activated by --lbtt), or Spin never claims (activated by -s or --spin). These three formats also support streaming, i.e., you can concatenate multiple automata (and even mix these three formats in the same stream), and the tools will be able to read and process them in sequence.

The other possible outputs are GraphViz output (-d or --dot), various statistics (--stats), or nothing at all (--quiet). It may seem strange to ask a tool to not output anything, but it makes sense when only the exit status matters (for instance using autfilt to check whether an input automaton has some property) or for timing purposes.

HOA output

Details about supported features of the HOA format can be found on a separate page.

The HOA output should be the preferred format to use if you want to pass automata between different tools. Since Spot 1.99.7, it is the default output format, but you can explicitely request it using the -H parameter and this allows passing additional options to the HOA printer.

Here is an example where ltl2tgba is used to construct two automata: one for a U b and one for (Ga -> Gb) W c.

ltl2tgba 'a U b' '(Ga -> Gb) W c'
HOA: v1
name: "a U b"
States: 2
Start: 1
AP: 2 "a" "b"
acc-name: Buchi
Acceptance: 1 Inf(0)
properties: trans-labels explicit-labels state-acc deterministic
properties: stutter-invariant terminal
--BODY--
State: 0 {0}
[t] 0
State: 1
[1] 0
[0&!1] 1
--END--
HOA: v1
name: "(Gb | F!a) W c"
States: 5
Start: 0
AP: 3 "b" "a" "c"
acc-name: Buchi
Acceptance: 1 Inf(0)
properties: trans-labels explicit-labels trans-acc stutter-invariant
--BODY--
State: 0
[!1&!2] 0 {0}
[2] 1
[0&1&!2] 2
[1&!2] 3
State: 1
[t] 1 {0}
State: 2
[0] 2 {0}
State: 3
[!1&!2] 0 {0}
[!1&2] 1
[1&!2] 3
[1&2] 4
State: 4
[!1] 1
[1] 4
--END--

The above output contains two automata, named after the formulas they represent. Here is a picture of these two automata:

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The HOA format supports both state and transition-based acceptance. Although Spot works only with transition-based acceptance, its output routines default to state-based acceptance whenever possible (this is the case in the first of these two automata) and use transition-based acceptance otherwise. You can change this behavior using -Hs (or --hoaf=s), -Ht, or -Hm. Option s corresponds to the default to use state-based acceptance whenever possible. Option t forces transition-based acceptance. For instance compare this output to the previous one:

ltl2tgba -Ht 'a U b'
HOA: v1
name: "a U b"
States: 2
Start: 1
AP: 2 "a" "b"
acc-name: Buchi
Acceptance: 1 Inf(0)
properties: trans-labels explicit-labels trans-acc deterministic
properties: stutter-invariant terminal
--BODY--
State: 0
[t] 0 {0}
State: 1
[1] 0
[0&!1] 1
--END--

Option m uses mixed acceptance, i.e, some states might use state-based acceptance while other will not:

ltl2tgba -Hm '(Ga -> Gb) W c'
HOA: v1
name: "(Gb | F!a) W c"
States: 5
Start: 0
AP: 3 "b" "a" "c"
acc-name: Buchi
Acceptance: 1 Inf(0)
properties: trans-labels explicit-labels stutter-invariant
--BODY--
State: 0
[!1&!2] 0 {0}
[2] 1
[0&1&!2] 2
[1&!2] 3
State: 1 {0}
[t] 1
State: 2 {0}
[0] 2
State: 3
[!1&!2] 0 {0}
[!1&2] 1
[1&!2] 3
[1&2] 4
State: 4
[!1] 1
[1] 4
--END--

It is also possible to output each automaton on a single line, in case the result should be used with line-based tools or embedded into a CSV file… Here is an example using both transition-based acceptance, and single-line output:

ltl2tgba -Htl 'a U b' '(Ga -> Gb) W c'
HOA: v1 name: "a U b" States: 2 Start: 1 AP: 2 "a" "b" acc-name: Buchi Acceptance: 1 Inf(0) properties: trans-labels explicit-labels trans-acc deterministic stutter-invariant terminal --BODY-- State: 0 [t] 0 {0} State: 1 [1] 0 [0&!1] 1 --END--
HOA: v1 name: "(Gb | F!a) W c" States: 5 Start: 0 AP: 3 "b" "a" "c" acc-name: Buchi Acceptance: 1 Inf(0) properties: trans-labels explicit-labels trans-acc stutter-invariant --BODY-- State: 0 [!1&!2] 0 {0} [2] 1 [0&1&!2] 2 [1&!2] 3 State: 1 [t] 1 {0} State: 2 [0] 2 {0} State: 3 [!1&!2] 0 {0} [!1&2] 1 [1&!2] 3 [1&2] 4 State: 4 [!1] 1 [1] 4 --END--

Finally, version 1.1 of the HOA format can be specified using the -H1.1 option. Version 1, which is currently the default, can also be requested explicitly using -H1. The main advantage of version 1.1, as far as Spot is concerned, is that some of negated properties can be transmitted. For instance, compare

ltl2tgba -f GFa -f FGa -H1 --check | grep -E '^(HOA|properties|name):'
HOA: v1
name: "GFa"
properties: trans-labels explicit-labels trans-acc complete
properties: deterministic stutter-invariant
HOA: v1
name: "FGa"
properties: trans-labels explicit-labels state-acc semi-deterministic
properties: stutter-invariant very-weak

versus

ltl2tgba -f GFa -f FGa -H1.1 --check | grep -E '^(HOA|properties|name):'
HOA: v1.1
name: "GFa"
properties: trans-labels explicit-labels trans-acc complete
properties: deterministic stutter-invariant !inherently-weak
HOA: v1.1
name: "FGa"
properties: trans-labels explicit-labels state-acc !complete
properties: !deterministic exist-branch !unambiguous semi-deterministic
properties: stutter-invariant very-weak !terminal

The --check option inspects the automata for additional properties such that their strength or whether they are stutter-invariant and unambiguous. You can see in this example that version 1.1 of the format carries additional negated properties that could not be represented in the first version.

LBTT output

The LBTT output has two flavors: state-based (which is used to output Büchi automata or monitors) or transition-based (for TGBA).

ltl2tgba --ba --lbtt 'p0 U p1'
2 1
0 1 -1
1 p1
0 & p0 ! p1
-1
1 0 0 -1
1 t
-1

If you want to request transition-based output even for Büchi automata, use --lbtt=t.

ltl2tgba --ba --lbtt=t 'p0 U p1'
2 1t
0 1
1 -1 p1
0 -1 & p0 ! p1
-1
1 0
1 0 -1 t
-1

Note that the LBTT output generalizes the format output by LBT with support for transition-based acceptance. Both formats however are restricted to atomic propositions of the form p0, p1, etc… In case other atomic propositions are used, Spot output them in double quotes. This other extension of the format is also supported by ltl2dstar.

ltl2tgba --ba --lbtt 'a U b'
2 1
0 1 -1
1 "b"
0 & "a" ! "b"
-1
1 0 0 -1
1 t
-1

Spin output

Spin never claims can be requested using -s or --spin. They can only represent Büchi automata, so these options imply --ba.

ltl2tgba -s 'a U b'
never { /* a U b */
T0_init:
  if
  :: (b) -> goto accept_all
  :: ((a) && (!(b))) -> goto T0_init
  fi;
accept_all:
  skip
}

Recent versions of Spin (starting with Spin 6.2.4) output never claims in a slightly different style that can be requested using either -s6 or --spin=6:

ltl2tgba -s6 'a U b'
never { /* a U b */
T0_init:
  do
  :: atomic { (b) -> assert(!(b)) }
  :: ((a) && (!(b))) -> goto T0_init
  od;
accept_all:
  skip
}

(Note that while Spot is able to read never claims that follow any of these two styles, it is not capable of interpreting an arbitrary piece of Promela syntax.)

Dot output

The -d or --dot option causes automata to be output in GraphViz's format.

ltl2tgba '(Ga -> Gb) W c' -d
digraph "(Gb | F!a) W c" {
  rankdir=LR
  label="Inf(0)\n[Büchi]"
  labelloc="t"
  node [shape="circle"]
  I [label="", style=invis, width=0]
  I -> 0
  0 [label="0"]
  0 -> 0 [label="!a & !c\n{0}"]
  0 -> 1 [label="c"]
  0 -> 2 [label="a & b & !c"]
  0 -> 3 [label="a & !c"]
  1 [label="1"]
  1 -> 1 [label="1\n{0}"]
  2 [label="2"]
  2 -> 2 [label="b\n{0}"]
  3 [label="3"]
  3 -> 0 [label="!a & !c\n{0}"]
  3 -> 1 [label="!a & c"]
  3 -> 3 [label="a & !c"]
  3 -> 4 [label="a & c"]
  4 [label="4"]
  4 -> 1 [label="!a"]
  4 -> 4 [label="a"]
}

Converting dot output to images or pdf

This output should be processed with dot to be converted into a picture. For instance use dot -Tpng or dot -Tpdf. The pictures on this page are produced with dot -Tsvg.

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Customizing the dot output

This output can be customized by passing optional characters to the --dot option. For instance v requests a vertical layout (instead of the default horizontal layout), c requests circle states, s causes strongly-connected components to be displayed, n causes the name (see below) of the automaton to be displayed, and a causes the acceptance condition to be shown as well. Option b causes sets to be ouput as bullets (e.g., ⓿ instead of {0}); option r (for rainbow) causes sets to be displayed in different colors, while option R also uses colors, but it chooses them depending on whether a set is used with Fin-acceptance, Inf-acceptance, or both. Option C(COLOR) can be used to color all states using COLOR, and the option f(FONT) is used to select a fontname: it is often necessary when b is used to ensure the characters ⓿, ❶, etc. are all selected from the same font.

ltl2tgba --dot=vcsna '(Ga -> Gb) W c'

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The acceptance condition is displayed in the same way as in the HOA format. Here Inf(0) means that runs are accepting if and only if they visit some the transitions in the set #0 infinitely often. For well known acceptance conditions (as Büchi in this case), their name is also displayed in bracket below.

The strongly connected components are displayed using the following colors:

  • green components contain an accepting cycle
  • red components contain no accepting cycle
  • black components are trivial (i.e., they contain no cycle)
  • gray components are useless (i.e., they are non-accepting, and are only followed by non-accepting components)

Here is an example involving all colors:

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The dot output can also be customized via two environment variables:

  • SPOT_DOTDEFAULT contains default arguments for the --dot option (for when it is used implicitly, or used as just --dot without argument). For instance after export SPOT_DOTDEFAULT=vcsn, using --dot is equivalent to --dot=vcsn. However using --dot=xyz (for any value of xyz, even empty) will ignore the SPOT_DOTDEFAULT variable. If the argument of --dot contains a dot character, then this dot is replaced by the contents of SPOT_DOTDEFAULT. So --dot=.A would be equivalent to --dot=vcsnA with our example definition of SPOT_DOTDEFAULT.
  • SPOT_DOTEXTRA may contains an arbitrary string that will be emitted in the dot output before the first state. This can be used to modify any attribute. For instance (except for this page, where we had do demonstrate the various options of --dot, and a few pages where we show the --dot output verbatim) all the automata displayed in this documentation are generated with the following environment variables set:
export SPOT_DOTDEFAULT='Brf(Lato)C(#ffffa0)'
export SPOT_DOTEXTRA='edge[arrowhead=vee, arrowsize=.7]'

Working with dot2tex

The dot2tex program interacts with GraphViz to convert dot files into TeX figures. The layout is still done by tools provided by GraphViz (i.e. dot, neato, circo, …) but the actual rendering is done using LaTeX with the TikZ or PSTricks packages. One advantage is that this allows embedding math formulas into the graph, something GraphViz alone cannot do. Another advantage is that you can then easily edit the LaTeX figure, for instance to add additional graphical elements.

The dot formater of Spot has an option x, that is convenient to use with dot2tex. This option causes labels to be rendered as LaTeX mathematical formulas instead of ASCII text.

ltl2tgba 'p0 U p1' --dot=x | dot2tex --autosize --nominsize > out.tex

The above command should give you a LaTeX file that compiles to the following figure:

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Here an example with bullets denoting acceptance sets, and SCCs:

ltl2tgba -G -D '!a & FGa' --dot=sbarx | dot2tex --autosize --nominsize > out.tex

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Caveats:

  • dot2tex should be called with option --autosize in order to compute the size of each label before calling GraphViz to layout the graph. This is because GraphViz cannot compute the correct size of mathematical formulas. Unfortunately, the release of dot2tex 2.9.0 contains a bug where sizes are intepreted as integers instead of floats. This can cause labels or shapes to disappear. This bug of dot2tex was fixed in 2014, but at the time of writing (summer 2017) no new release of dot2tex has been made. To work around this, make sure you install dot2tex from its git repository:

    git clone https://github.com/kjellmf/dot2tex.git
    cd dot2tex
    sudo python setup.py install
    
  • The default size of nodes seems slightly too big for our usage. Using --nominsize is just one way around it. Refer to the dot2tex manual for finer ways to set the node size.

Statistics

The --stats option takes a format string parameter to specify what and how statistics should be output.

Most tools support a common set of statistics about the output automaton (like %s for the number of states, %t for transitions, %e for edges, etc.). Additional statistics might be available depending on what the tool does (for instance autfilt also uses capitaized letters %S, %T, and %E to display the same statistics about the input automaton). All the available statistics are displayed when a tool is run with --help.

For instance here are the statistics available in randaut:

%%                         a single %
%a                         number of acceptance sets
%c, %[LETTERS]c            number of SCCs; you may filter the SCCs to count
                           using the following LETTERS, possibly
                           concatenated: (a) accepting, (r) rejecting, (c)
                           complete, (v) trivial, (t) terminal, (w) weak,
                           (iw) inherently weak. Use uppercase letters to
                           negate them.
%d                         1 if the output is deterministic, 0 otherwise
%e                         number of reachable edges
%F                         seed number
%g, %[LETTERS]g            acceptance condition (in HOA syntax); add brackets
                           to print an acceptance name instead and LETTERS to
                           tweak the format: (0) no parameters, (a)
                           accentuated, (b) abbreviated, (d) style used in
                           dot output, (g) no generalized parameter, (l)
                           recognize Street-like and Rabin-like, (m) no main
                           parameter, (p) no parity parameter, (o) name
                           unknown acceptance as 'other', (s) shorthand for
                           'lo0'.
%h                         the automaton in HOA format on a single line (use
                           %[opt]h to specify additional options as in
                           --hoa=opt)
%L                         automaton number
%m                         name of the automaton
%n                         number of nondeterministic states in output
%p                         1 if the output is complete, 0 otherwise
%r                         wall-clock time elapsed in seconds (excluding
                           parsing)
%R, %[LETTERS]R            CPU time (excluding parsing), in seconds; Add
                           LETTERS to restrict to(u) user time, (s) system
                           time, (p) parent process, or (c) children
                           processes.
%s                         number of reachable states
%t                         number of reachable transitions
%u, %[e]u                  number of states (or [e]dges) with universal
                           branching
%u, %[LETTER]u             1 if the automaton contains some universal
                           branching (or a number of [s]tates or [e]dges with
                           universal branching)
%w                         one word accepted by the output automaton
%x, %[LETTERS]x            number of atomic propositions declared in the
                           automaton;  add LETTERS to list atomic
                           propositions with (n) no quoting, (s) occasional
                           double-quotes with C-style escape, (d)
                           double-quotes with C-style escape, (c)
                           double-quotes with CSV-style escape, (p) between
                           parentheses, any extra non-alphanumeric character
                           will be used to separate propositions

In most tools %F and %L are the input filename and line number, but as this makes no sense in randaut, these two sequences emit numbers related to the generation of automata.

For instance let's generate 1000 random automata with 100 states and density 0.2, and just count the number of edges in each automaton. Then use R to summarize the distribution of these values:

randaut -e0.2 -Q100 -n1000 a --stats %e > size.csv
Rscript -e "summary(read.csv('size.csv', header=FALSE, col.names='edges'))"
    edges     
Min.   :1939  
1st Qu.:2056  
Median :2083  
Mean   :2082  
3rd Qu.:2107  
Max.   :2233  

For \(Q=100\) states and density \(D=0.2\) the expected degree of each state is \(1+(Q-1)D = 1+99\times 0.2 = 20.8\), so the expected number of edges should be \(20.8\times100=2080\).

Timing

Two of the statistics are related to time: %r displays wall-clock time, while %R displays CPU-time.

genltl --or-gf=1..8 | ltl2tgba --high --stats='%f,%r,%R'
GFp1,0.00080795,0
GF(p1 | p2),0.00121359,0
GF(p1 | p2 | p3),0.002187,0
GF(p1 | p2 | p3 | p4),0.00451728,0.01
GF(p1 | p2 | p3 | p4 | p5),0.0108164,0.01
GF(p1 | p2 | p3 | p4 | p5 | p6),0.041465,0.05
GF(p1 | p2 | p3 | p4 | p5 | p6 | p7),0.224413,0.22
GF(p1 | p2 | p3 | p4 | p5 | p6 | p7 | p8),1.1064,1.1

Note that %r is implemented using the most precise clock available and usually has nano-second precision, while %R uses the times() system call (when available) and is usually only precise up to 1/100 of a second. However, as a wall-clock time, %r will also be affected by the load of the machine: if a machine is overloaded, or swapping a lot, you may notice a wall-clock time that is significantly higher than the CPU time measured by %R.

Additional arguments may be passed to %R to select the time that must be output. By default, this the CPU-time spent in both user code and system calls. This can be restricted using one of u (user) or s (system). Also by default this includes the CPU-time for the current process and any of its children: adding p (parent) and c (children) will show only the selected time. Note that few tools actually execute other processes: autfilt and ltl2tgba can do so when calling a SAT solver for SAT-based minimization, and ltldo will obviously call any listed tool. However in the case of ltldo the measured time is that of executing the other tools, so the result of %[p]R is likely to be always 0.

Here is an example where we use ltldo to benchmark the (default) --high option of ltl2tba against the --low option, computing for each option the overall wall-clock time, CPU-time spent in ltldo, and CPU-time spent in ltl2tgba:

genltl --or-gf=1..8 |
ltldo '{high}ltl2tgba' '{low}ltl2tgba --low' --stats='%T,%f,%r,%[p]R,%[c]R'
high,GFp1,0.0256914,0,0.03
low,GFp1,0.0227265,0,0.03
high,GFp1 | GFp2,0.027385,0,0.04
low,GFp1 | GFp2,0.0251961,0,0.02
high,GFp1 | GFp2 | GFp3,0.0263832,0,0.03
low,GFp1 | GFp2 | GFp3,0.0268066,0,0.03
high,GFp1 | GFp2 | GFp3 | GFp4,0.0316787,0,0.03
low,GFp1 | GFp2 | GFp3 | GFp4,0.0262329,0,0.04
high,GFp1 | GFp2 | GFp3 | GFp4 | GFp5,0.0362886,0,0.03
low,GFp1 | GFp2 | GFp3 | GFp4 | GFp5,0.0251995,0,0.03
high,GFp1 | GFp2 | GFp3 | GFp4 | GFp5 | GFp6,0.0672614,0,0.07
low,GFp1 | GFp2 | GFp3 | GFp4 | GFp5 | GFp6,0.0254365,0,0.03
high,GFp1 | GFp2 | GFp3 | GFp4 | GFp5 | GFp6 | GFp7,0.213139,0,0.22
low,GFp1 | GFp2 | GFp3 | GFp4 | GFp5 | GFp6 | GFp7,0.0286718,0,0.03
high,GFp1 | GFp2 | GFp3 | GFp4 | GFp5 | GFp6 | GFp7 | GFp8,1.09342,0,1.09
low,GFp1 | GFp2 | GFp3 | GFp4 | GFp5 | GFp6 | GFp7 | GFp8,0.0293516,0,0.03

Naming automata

Automata can be given names. This name can be output in the HOA format, but also in GraphViz output when --dot=n is given.

By default, ltl2tgba will use the input formula as name. Other tools have no default name. This name can be changed using the --name option, that takes a format string similar to the one of --stats.

ltl2tgba --name='TGBA for %f' --dot=n 'a U b'

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If you have an automaton saved in the HOA format, you can extract its name using autfilt --stats=%M input.hoa. The %M escape sequence is replaced by the name of the input automaton.

Here is a pipeline of commands that generates five LTL formulas \(\varphi\) such that both \(\varphi\) and \(\lnot\varphi\) are translated into a 3-state TGBA by ltl2tgba. It starts by generating an infinite stream of random LTL formulas using a and b as atomic propositions, then it converts these formulas as TGBA (in the HOA format, therefore carrying the formula as name), filtering only the TGBA with 3 states and outputting !(%M) (that is the negation of the associated formula), translating the resulting formulas as TGBA, again retaining only the names (i.e. formulas) of the automata with 3 states, and finally restricting the output to the first 5 matches using autfilt -n5.

randltl -n -1 a b |
ltl2tgba |
autfilt --states=3 --stats='!(%M)' |
ltl2tgba |
autfilt --states=3 --stats=%M -n5
G(b | F(b & Fa))
(!a | b | (!b & (b W Ga))) & (a | (!b & (b | (!b M F!a))))
(!a | (!a R b)) & (a | (a U !b))
!a & F((!a | FG!a) & (a | GFa))
X(!b W a)

Note that the above result can also be obtained without using autfilt and automata names. We can use the fact that ltl2tgba --stats can output the automaton size, and that ltl2tgba is also capable of reading from a CSV file (-F-/2 instructs ltl2tgba to read the standard input as if it was a CSV file, and to process its second column):

randltl -n -1 a b |                 # generate a stream of random LTL formulas
ltl2tgba -F- --stats='%s,!(%f)' |   # for each formula output "states,negated formula"
grep '^3,' |                        # keep only formulas with 3 states
ltl2tgba -F-/2 --stats='%s,%f' |    # for each negated formula output "states,formula"
grep '^3,' |                        # keep only negated formulas with 3 states
head -n5 | cut -d, -f2              # return the five first formulas
G(b | F(b & Fa))
(!a | b | (!b & (b W Ga))) & (a | (!b & (b | (!b M F!a))))
(!a | (!a R b)) & (a | (a U !b))
!a & F((!a | FG!a) & (a | GFa))
X(!b W a)

Note that the -F- argument in the first call to ltl2tgba is superfluous as the tool default to reading from its standard input. But we put it there for symmetry with the second call.

Naming output

By default, all output is sent to standard output, so you can either redirect it to a file, or pipe it to another program. You can also use the --output (a.k.a. -o) option to specify a filename where automata should be written. The advantage over a shell redirection, is that you may build a name using the same escape sequences as used by --stats and --name.

For instance %d is replaced by 0 or 1 depending on whether the automaton is deterministic. We can generate 20 random automata, and output them in two files depending on their determinism:

randaut -n 20 -Q2 -e1 1 -o out-det%d.hoa
autfilt -c out-det0.hoa    # Count of non-deterministic automata
autfilt -c out-det1.hoa    # Count of deterministic automata
14
6

If you use this feature, beware that the output filename is only truncated once a first automaton is output to it: so if no automaton is output for a given filename, the existing file will be left untouched. For instance if we run the above commands again, but forcing randaut to output 20 deterministic automata, it may look like we produced more than 20 automata:

randaut -D -n 20 -Q2 -e1 1 -o out-det%d.hoa
autfilt -c out-det0.hoa    # Count of non-deterministic automata
autfilt -c out-det1.hoa    # Count of deterministic automata
14
20

This is because the out-det0.hoa file hasn't changed from the previous execution, while out-det1.hoa has been overwritten.

In the case where you want to append to a file instead of overwriting it, prefix the output filename with >> as in

randaut -D -n 20 -Q2 1 -o '>>out-det%d.hoa'

(You need the quotes so that the shell does not interpret >>.)