man aer (5): aegis report script language definition

DESCRIPTION

This manual entry describes the report generator script language used by the aer(1) command. The language resembles C, with a touch of awk and perl for flavour. It also closely resembles the appearance of aegis' database files.

This language grew out of the need to have a general purpose programming language to describe reports, and yet be as familiar as possible to the people who will be using it.

WORDS AND SYMBOLS

This section describes the various words and symbols understood by the language.

Names

A name is a contiguous set of alphanumeric characters, including underscore (_). It must not start with a digit. Names may be of any length. Names are case sensitive, so uppercase and lowercase letters are unique.

Here are some examples of names

print	sqrt	if
how_long	UpperCase	dig57

Some words are reserved as keywords. These are the words which appear in bold in the statement descriptions, below.

Integer Constants

An integer constant may be decimal, any sequence of digits. Constants may be octal, any sequence of octal digits starting with a zero. Constant may be hexadecimal, any sequence of hexadecimal digits, starting with a 0x prefix. These are represented by the internal long type, so significance is limited.

Here are some examples of integer constants:

43	015	0xbeEf
2147483647	017777777777	0x7FFFFFFF

Floating Point Constants

A floating point constant has an integer part, a fraction part and an exponent part.

Here are some examples of floating point constants:

1.2e3	4.2e+1	1.628e-94
0.567	5e6	.67

String Constants

A string constant is represented as characters within double quotes ("). All characters in the script file are required to be printable, so special characters are represented by escape sequences. These escape sequences are:

\"	the `"` character
\\	the `\` character
\n	Newline
\f	Form Feed
\r	Carriage Return
\b	Backspace
\t	Horizontal Tab
\nnn	octal character value

Here are some examples of string constants:

"Hello, World!"	"Go away"	""
"The End	"slosh is \\"	"Say \"Please\""

Symbols

The non-alphanumeric characters are used to represent symbols, usually expression operators or statement terminators. The symbols used include:

!	!=	!~	##	##=
%	%=	&	&&	&=
(	)	*	**	**=
*=	+	++	+=	,
-	--	-=	.	/
/=	:	;	<	<<
<<=	<=	=	==	>
>=	>>	>>=	?	[
]	^	^=	{	\|
\|=	\|\|	}	~	~~

White Space

White space serves to separate words and symbols, and has no other significance. The language is free-form. White space includes the SPACE, TAB, FF, and NEWLINE characters.

Comments

Comments are delimited by /* and */ pairs, and are treated as a single white space character.

STATEMENTS

Statement serve to control the flow of execution of the program, or the existence of variables.

The Expression Statement

The commonest statement consists of an expression terminated by a semicolon. The expression is evaluated, and any result is discarded.

Examples of this statement include

x = 42;
print("Hello, World!);

The If Statement

The if statement is used to conditionally execute portions of code. Examples if the if statement include:

if (x == 42)
     x = 1;
if (x * x < 1)
     print("no");
else
     print("yes");

The For Statement

The for statement has two forms. The first form is described as

for (expr1; expr2; expr3)
     stmt

The expr1 is done before the loop begins. The expr2 controls, the loop; if it does not evaluate to true the loop terminates. The loop body is the stmt. The loop increment is done by the expr3, and the the test is performed again.

Each of the expressions is optional; any or all may be omitted.

Here is an example of a for loop:

for (j = 0; j < 10; ++j)
     print(j);

The second form of the for statement looks like this:

for (name in keys(passwd))
     print(name, passwd[name].pw_comment);

The Break Statement

The break statement is used to break out of a loop.

Here is an example of a break statement:

for (j = 0; ; j = 2 * j + 4)
{
     print(j);
     if (j >= 0x800)
          break;
}

The break statement works within all loop statements.

The Continue Statement

The continue statement is used to terminate the loop body and start another repetition.

Here is an example of a continue statement:

for (j = 0; j < 1000; j = 2 * j + 4)
{
     if (j < 42)
          continue;
     print(j);
}

The continue statement works within all loop statements.

The While Statement

The while statement is another loop construct. The condition is evaluated before the loop body.

line = 0;
while (line < 7)
{
     print("");
     ++line;
}

The Do Statement

The do statement is another loop construct. The condition is evaluate after the loop body.

do
     print("yuck");
while
     (line++ < 7);

The Compound Statement

The compound statement is a way of grouping other statements together. It is enclosed in curly braces.

if ( lines < 7)
{
     print("This\n");;
     print("could\n");;
     print("have\n");;
     print("been\n");;
     print("seven\n");;
     print("blank\n");;
     print("lines.\n");;
}

The Local Statement

The auto statement is used to declare variables and initialize them to be nul.

auto x, y, z;
x = 42;

All user-defined variables must be declared before they are used.

The Null Statement

The null statement does nothing. It consists of a single semicolon. It is most often seen as a loop body.

for (n = 0, bit = 1; n < bit_num; ++n, bit <<= 1)
     ;

The Try Catch Statement

The try catch statement is used to catch errors which would usually cause the report to fail.

try
     statement1
catch (variable)
     statement2

The first statement is executed. If no error occurs, nothing else is done. If an error occurs in the execution of the first statement the firsdt statement execution is terminated and then the given variable is set to a description of the error and the second statement is executed.

EXPRESSIONS

Expressions are much the same as in C, using the same operators. The following table describes operator precedence and associativity:

[ ]	subscripting	value [ expr ]
( )	function call	expr ( expr_list )
( )	grouping	( expr )

++	post increment	lvalue ++
++	pre increment	++lvalue
--	post decrement	lvalue --
--	pre decrement	--lvalue
~	compliment	~ expr
!	not	! expr
-	unary minus	- expr
+	unary plus	+ expr

exponentiation

expr ** expr

*	multiply	expr * expr
/	divide	expr / expr
%	modulo (remainder)	expr % expr
~~	matches	expr ~~ expr
!~	does not match	expr !~ expr
in	list member	expr in expr

+	addition (plus)	expr + expr
-	subtraction (minus)	expr - expr
##	list and string join	expr ## expr

<<	shift left	expr << expr
>>	shift right	expr >> expr

<	less than	expr < expr
<=	less than or equal	expr <= expr
>	greater than	expr > expr
>=	greater than or equal	expr >= expr

==	equal	expr == expr
!=	not equal	expr != expr

bitwise AND

expr & expr

bitwise exclusive OR

expr ^ expr

bitwise inclusive OR

expr | expr

? :

arithmetic if

expr ? expr : expr

=	simple assignment	expr = expr
*=	multiply and assign	expr = expr*
/=	divide and assign	expr /= expr
%=	modulo and assign	expr %= expr
+=	add and assign	expr += expr
-=	subtract and assign	expr -= expr
<<=	shift left and assign	expr <<= expr
>>=	shift right and assign	expr >>= expr
&=	AND and assign	expr &= expr
^=	exclusive OR and assign	expr ^= expr
\|=	inclusive OR and assign	expr \|= expr

comma (sequencing)

expr , expr

Most of these operators behave as they do in C, but some of these operators will require some explanation.

Exponentiation

The ** operator raises the left argument to the right'th power. It is right associative.

Match

The ~~ operator compares two strings. It returns a number between 0.0 and 1.0. Zero means completely different, one means identical. Case is significant.

Not Match

The !~ is used to compare two strings, and returns the opposite of the ~~ operator; one if completely different, and zero if identical.

String Join

The ## operator is used to join two strings together.

TYPES

There are several types used within the report language.

array: Values of this type contain other values, indexed by a string. If you attempt to index by an arithmetic type, it will be silently converted to a string. Use the keys function to determine all of the keys; use the count function to determine how many entries an array has. The type of an array element is not restricted, only the index must be a string.
boolean: This type has two values: true and false. These value arise from the boolean operators described earlier.
integer: This type is represented by the long C type. It has a limited range of values (usually -2e9 to 2e9 approximately). If used in a string context, it will be silently converted to a string. For exact control of the format, used the sprintf function.
list: Values of this type contain a list of other values. The type of these values is not restricted. The array index operator (e[e]) may be used to access list elements; indexes start at zero (0).
string: Values of this type are an arbitrary string of C characters, except the NUL character ( ). Strings may be of any length.
struct: Values of this type contain additional values. These values are accessed using the "dot" operator. These values may also be treated as if they were arrays.
real: This type is represented the the double C type. If used in a string context, it will be silently converted to a string. For exact control of the format, used the sprintf function.

FUNCTIONS

There are a number of built-in functions.

basename

This function is used to extract the last element from a file path.

capitalize

This function converts it argument to a capitalized string in Title Case.

ceil

This function is used to round a number to an integer, towards positive infinity.

change_number

This function is used to determine the change number. It may be set by the -Change command line option, or it may default. The return value is an integer.

change_number_set

This function maybe used to determine if the change number was set by the -Change command line option. The return value is a boolean.

columns

This function is used to define the report columns. Each argument is a structure containing some or all of the following fields:

left	the left margin, counting characters from 0 on the left
right	the right margin, plus one
width	the width in characters, defaults to 7 if right not specified
padding	white space between columns, defaults to 1 if not set
title	the title for this column, separate multiple lines with \n

The columns must be defined before the print function is used.

count

This function is used to count the number of elements in a list or array.

dirname

This function is used to extract all but the last element from a file path.

downcase

This functions converts its argument to lower case.

eject

This function is used to start a new page of output.

floor

This function is used to round a number to an integer, towards negative infinity.

getenv

This function is used to get the value of an environment variable. Will return the empty string if not set.

gettime

This function is used to parse a string to produce a time. It understands a variety of different date formats.

getuid

This function takes no arguments, and returns the user ID of the process which invoked the report generator. The return value is an integer.

keys

This function may be given an array or a list as argument. It returns a list of keys which may be used to index the argument. Most often seen in for loops.

length

This function is used to find the length of a string.

mktime

This a synonym for the gettime function.

mtime

This function may be used to obtain the modification time of a file.

need

This function is used to insert a page break into the report if the required number of lines is not available before the end of page. If sufficient lines are available, only a single blank line will be inserted. The return value is void.

now

This function takes no arguments, and returns the current time.

page_length

This function may be used to determine the length of the output page in lines. The return value is an integer.

page_width

This function may be used to determine the width of the output page in columns. The return value is an integer.

print

This function is used to print into the defined columns. Columns will wrap around.

project_name

This function is used to determine the project name. It may be set by the -Project command line option, or it may default. The return value is a string.

project_name_set

This function maybe used to determine if the project name was set by the -Project command line option. The return value is a boolean.

quote_html

This function quotes its argument string to insulate HTML special characters; these include "less than" (<), "ampersand" (&) and non-printing characters. This is most often used to generate suitable text for web pages.

quote_tcl

This function quotes its argument string to insulate TCL special characters; these include "[]" and non-printing characters. This is most often used to generate suitable text for TCL interface scripts.

quote_url

This function quotes its argument string to insulate URL special characters; these include "?+#:&=" and non-printing characters. This is most often used to generate suitable text for web pages.

round

This function is used to round a number to an integer, towards the closest integer.

sort

This function must be given a list as argument. The values are sorted into ascending order. A new list is returned.

split

This function is used to split a string into a list of strings. The first argument is the string to split, the second argument is the character to split around.

sprintf

This function is used to build strings. It is similar to the sprintf(3) function.

strftime

This function is used to format times as strings. The first argument is the format string, the second argument is a time. See the strftime(3) man page for more the format specifiers.

subst

This function is used to substitute strings by regular expression. The first argument is the pattern to match, the second argument is the substitution pattern, the third argument is the input string to be substituted. The option fourth argument is the number of substitutions to perform; the default is as many as possible.

substr

This function is used to extract substrings from strings. The first argument is a string, the second argument is the starting position, starting from 0, and the third argument is the length.

terse

This function may be used to determine of the -TERse command line option was used. The return type is a boolean.

title

This function is used to set the title of the report. It takes at most two arguments, one for each available title line.

trunc

This function is used to round a number to an integer, towards zero.

typeof

This function is used to determine the type of a value. The return type is a string containing the name of the type, as described in the

unquote_url

This function will remove URL quoting from the argument string. URL quoting takes the form of a percent sign (%) followed by two hex digits. This is replaced by a single character with the value represented by the hex digits.

upcase

This functions converts its argument to upper case.

working_days

This function is used to determine the number of working days between two times.

wrap

This function is used to wrap a string into a list of strings. The first argument is the wring to wrap, the second argument is the maxmium width of the output strings.

wrap_html

This function is used to wrap a string into a list of strings. The first argument is the wring to wrap, the second argument is the maxmium width of the output strings. This is very similar to the wrap functions, except thatit inserts HTML paragraph breaks <p> or line breaks <br> to reflect the newlines within the string (2 or 1, respectively). TYPES section.

VARIABLES

There are a number of built-in variables.

arg

This variable is a list containing the arguments passed on the aer(1) command line.

change

There is a special type of variable created by using an expression similar to project[project_name()].state.change[n] which contains all of the fields described in aecstate(5), plus some extras:

change: Branches have a change array, just like project below.
change_number: The number of the change.
config: This gives access to all of the fields described in aepconfgP(5).
project_name: The name of the project containing the change.
src: This gives access to the change files, and when indexed by file name, yields a value conataining fields as described in aefstate

group

This variable is an array containing all of the entries in the /etc/group file. Each entry is a structure with fields as documented in the group(5) manual entry. The gr_mem element is a list of strings. This array may be indexed by either a string, treated as a group name, or by an integer, treated as a GID.

passwd

This variable is an array containing all of the entries in the /etc/passwd file. Each entry is a structure with fields as documented in the passwd(5) manual entry. This array may be indexed by either a string, treated as a user name, or by an integer, treated as a uid.

project

This variable is an array containing one entry for each aegis project, indexed by name. Each array element is a structure, containing

name	the project name
directory	the root of the project directory tree
state	the project state

The project state contains the fields documented in the aepstate(5) manual entry. Except: the change field is not a list of change numbers, it is an array indexed by change number of change states, as documented in the aecstate(5) manual entry. (See change, above.)

user

This variable is an array containing the .aegisrc file of each user. Each entry is a structure with fields as documented in the aeuconf(5) manual entry. This array may be indexed by either a string, treated as a user name, or by an integer, treated as a uid. Files which are unreadable or absent will generate an error, so you need to wrap accesses in a try/catch statement. (Note: count() and keys() functions think the array is empty; if you want a list of users, consult the passwd array.)

FILES

The reports are kept in the /usr/share/aegis/report directory. The reports are associated with a name by the /usr/share/aegis/report.index file. Their names use the command line argument abbreviation scheme, so that report names may be abbreviated.

COPYRIGHT

The aegis program comes with ABSOLUTELY NO WARRANTY; for details use the 'aegis -VERSion License' command. This is free software and you are welcome to redistribute it under certain conditions; for details use the 'aegis -VERSion License' command.

AUTHOR

Peter Miller	E-Mail:	[email protected]
`/\/\*`	WWW:	http://www.canb.auug.org.au/~millerp/