aer(5)

NAME
aer - 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 ' 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 aepconf(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(5), for the src field.

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

SEE ALSO

aer(1)
    report generator

aecstate(5)
    change state description

aepstate(5)
    project state description

aerptidx(5)
    report index file format