States is an awk-alike text processing tool with some state
machine extensions. It is designed for program source code
highlighting and to similar tasks where state information helps input
processing.
At a single point of time, States is in one state, each quite
similar to awk's work environment, they have regular expressions which
are matched from the input and actions which are executed when a match
is found. From the action blocks, states can perform state
transitions; it can move to another state from which the processing is
continued. State transitions are recorded so states can return
to the calling state once the current state has finished.
The biggest difference between states and awk, besides state
machine extensions, is that states is not line-oriented. It
matches regular expression tokens from the input and once a match is
processed, it continues processing from the current position, not from
the beginning of the next input line.
OPTIONS
-D var=val, --define=var=val
Define variable var to have string value val. Command
line definitions overwrite variable definitions found from the config
file.
-f file, --file=file
Read state definitions from file file. As a default,
states tries to read state definitions from file states.st
in the current working directory.
-h, --help
Print short help message and exit.
-o file, --output=file
Save output to file file instead of printing it to
stdout.
-p path, --path=path
Set the load path to path. The load path defaults to the
directory, from which the state definitions file is loaded.
-s state, --state=state
Start execution from state state. This definition overwrites
start state resolved from the start block.
-v, --verbose
Increase the program verbosity.
-V, --version
Print states version and exit.
-W level, --warning=level
Set the warning level to level. Possible values for level
are:
light
light warnings (default)
all
all warnings
STATES PROGRAM FILES
States program files can contain on start block,
startrules and namerules blocks to specify the initial
state, state definitions and expressions.
The start block is the main() of the states program, it is
executed on script startup for each input file and it can perform any
initialization the script needs. It normally also calls the
check_startrules() and check_namerules() primitives which
resolve the initial state from the input file name or the data found
from the begining of the input file. Here is a sample start block
which initializes two variables and does the standard start state
resolving:
Once the start block is processed, the input processing is continued
from the initial state.
The initial state is resolved by the information found from the
startrules and namerules blocks. Both blocks contain
regular expression - symbol pairs, when the regular expression is
matched from the name of from the beginning of the input file, the
initial state is named by the corresponding symbol. For example, the
following start and name rules can distinguish C and Fortran files:
If these rules are used with the previously shown start block,
states first check the beginning of input file. If it has
string -*- c -*-, the file is assumed to contain C code and the
processing is started from state called c. If the beginning of
the input file has string -*- fortran -*-, the initial state is
fortran. If none of the start rules matched, the name of the
input file is matched with the namerules. If the name ends to suffix
c or C, we go to state c. If the suffix is
f or F, the initial state is fortran.
If both start and name rules failed to resolve the start state,
states just copies its input to output unmodified.
The start state can also be specified from the command line with
option -s, --state.
State definitions have the following syntax:
state { expr {statements} ... }
where expr is: a regular expression, special expression or
symbol and statements is a list of statements. When the
expression expr is matched from the input, the statement block
is executed. The statement block can call states' primitives,
user-defined subroutines, call other states, etc. Once the block is
executed, the input processing is continued from the current intput
position (which might have been changed if the statement block called
other states).
Special expressions BEGIN and END can be used in the place
of expr. Expression BEGIN matches the beginning of the
state, its block is called when the state is entered. Expression
END matches the end of the state, its block is executed when
states leaves the state.
If expr is a symbol, its value is looked up from the global
environment and if it is a regular expression, it is matched to the
input, otherwise that rule is ignored.
The states program file can also have top-level expressions,
they are evaluated after the program file is parsed but before any
input files are processed or the start block is evaluated.
PRIMITIVE FUNCTIONS
call (symbol)
Move to state symbol and continue input file processing from
that state. Function returns whatever the symbol state's
terminating return statement returned.
calln (name)
Like call but the argument name is evaluated and its value
must be string. For example, this function can be used to call a
state which name is stored to a variable.
check_namerules ()
Try to resolve start state from namerules rules. Function
returns 1 if start state was resolved or 0 otherwise.
check_startrules ()
Try to resolve start state from startrules rules. Function
returns 1 if start state was resolved or 0 otherwise.
concat (str, ...)
Concanate argument strings and return result as a new string.
float (any)
Convert argument to a floating point number.
getenv (str)
Get value of environment variable str. Returns an empty string
if variable var is undefined.
int (any)
Convert argument to an integer number.
length (item, ...)
Count the length of argument strings or lists.
list (any, ...)
Create a new list which contains items any, ...
panic (any, ...)
Report a non-recoverable error and exit with status 1. Function
never returns.
print (any, ...)
Convert arguments to strings and print them to the output.
range (source, start, end)
Return a sub-range of source starting from position start
(inclusively) to end (exclusively). Argument source can
be string or list.
regexp (string)
Convert string string to a new regular expression.
regexp_syntax (char, syntax)
Modify regular expression character syntaxes by assigning new
syntax syntax for character char. Possible values for
syntax are:
'w'
character is a word constituent
' '
character isn't a word constituent
regmatch (string, regexp)
Check if string string matches regular expression regexp.
Functions returns a boolean success status and sets sub-expression
registers $n.
regsub (string, regexp, subst)
Search regular expression regexp from string string and
replace the matching substring with string subst. Returns the
resulting string. The substitution string subst can contain
$n references to the n:th parenthesized
sup-expression.
regsuball (string, regexp, subst)
Like regsub but replace all matches of regular expression
regexp from string string with string subst.
require_state (symbol)
Check that the state symbol is defined. If the required state
is undefined, the function tries to autoload it. If the loading
fails, the program will terminate with an error message.
split (regexp, string)
Split string string to list considering matches of regular
rexpression regexp as item separator.
sprintf (fmt, ...)
Format arguments according to fmt and return result as a
string.
strcmp (str1, str2)
Perform a case-sensitive comparision for strings str1 and
str2. Function returns a value that is:
-1
string str1 is less than str2
0
strings are equal
1
string str1 is greater than str2
string (any)
Convert argument to string.
strncmp (str1, str2, num)
Perform a case-sensitive comparision for strings str1 and
str2 comparing at maximum num characters.
substring (
str, start, end)
Return a substring of string str starting from position
start (inclusively) to end (exclusively).
BUILTIN VARIABLES
$.
current input line number
$n
the n:th parenthesized regular expression sub-expression from the
latest state regular expression or from the regmatch primitive
$`
everything before the matched regular rexpression. This is usable
when used with the regmatch primitive; the contents of this
variable is undefined when used in action blocks to refer the data
before the block's regular expression.
$B
an alias for $`
argv
list of input file names
filename
name of the current input file
program
name of the program (usually states)
version
program version string
FILES
/usr/share/enscript/hl/*.st enscript's states definitions
