NAME
states - awk alike text processing tool
SYNOPSIS
states [-hvV] [-D var=val] [-f file] [-o outputfile] [-p path] [-s
startstate] [-W level] [filename ...]
DESCRIPTION
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
beginning of the input file. Here is a sample start block which
initializes two variables and does the standard start state resolving:
start
{
a = 1;
msg = "Hello, world!";
check_startrules ();
check_namerules ();
}
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:
namerules
{
/\.(c|h)$/ c;
/\.[fF]$/ fortran;
}
startrules
{
/-\*- [cC] -\*-/ c;
/-\*- fortran -\*-/ fortran;
}
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
SEE ALSO
awk(1), enscript(1)
AUTHOR
Markku Rossi <mtr@iki.fi> <http://www.iki.fi/~mtr/>
GNU Enscript WWW home page: <http://www.iki.fi/~mtr/genscript/>