Open System Services Shell and Utilities Reference Manual (G06.29+, H06.08+, J06.03+)

lex(1) OSS Shell and Utilities Reference Manual
dashes ( - ) are not permitted. Unlike regexp names, state names share the C
#define namespace. In the rules section, states are recognized as <state> (state
within angle brackets).
The %x directive names exclusive states. When a scanner is in an exclusive
state, only rules prefixed with that state are active. Inclusive states are named
with the %s directive.
%{ or %} When placed on lines by themselves, enclose C code to be passed verbatim into
the global definitions of the output file. Such lines commonly include preproces-
sor directives and declarations of external variables and functions.
space or tab Appear at the beginning of lines in the definitions section that are to be passed
directly into the lex.yy.c output file, as part of the initial global definitions.
The rules section follows the definitions, separated by a line consisting of %%. The rules sec-
tion contains rules for matching input and taking actions, in the following format:
pattern [ action ]
pattern starts in the first column of the line and extends until the first nonescaped white space
character. The command attempts to find the pattern that matches the longest input sequence
and execute the associated action. If two or more patterns match the same input, the one that
appears first in the rules section is chosen. If no action exists, the matched input is discarded. If
no pattern matches the input, the default action is to copy it to the standard output file.
All action code is placed in the yylex() function. Text (C code or declarations) placed at the
beginning of the rules section is copied to the beginning of the yylex() function and can be used
in actions. This text must begin with a space or a tab (to distinguish it from rules). In addition,
any input (beginning with a space or within %{ and %} delimiter lines) appearing at the begin-
ning of the rules section before any rules are specified is written to file lex.yy.c after the declara-
tions of variables for the yylex() function and before the first line of code in yylex().
Elements of each rule are:
state A pattern can begin with a comma-separated list of state names enclosed by
angle brackets (< state [,state...] >). These states are entered through the BEGIN
statement. If a pattern begins with a state, the scanner can recognize it only
when in that state. The initial state is 0 (zero).
regexp A pattern can be a regular expression to match against the input stream. The
regular expressions in the lex command provides a rich character-matching syn-
tax.
The following characters, shown in order of decreasing precedence, have special
meanings:
x Matches the character x.
"" (double quotes)
Enclose characters and treat them as literal strings. For example, "*+"
is treated as the asterisk character followed by the plus character.
\str (backslash)
If str is one of the characters a, b, f, n, r, t,orv,
then represents the
ANSI C interpretation (for example, \n is a newline). If str is a string
of octal digits, it is interpreted as a character with octal value str.Ifstr
is a string of hexadecimal digits with a leading x, it is interpreted as a
character with that value. Otherwise, it is interpreted literally with no
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