Mikroelektronika MIKROE-742 데이터 시트

You can specify a series of alternatives for a pattern using 

"

|" 

to separate them,

so that 

will match any of 

"

bit", "bat"

, or 

"

bot"

in the target string

as would 

"

b(i|a|o)t)"

. The first alternative includes everything from the last pat-

tern delimiter 

("(", "["

, or the beginning of the pattern) up to the first 

"

|"

, and the

last alternative contains everything from the last 

"

|"

to the next pattern delimiter.

For this reason, it's common practice to include alternatives in parentheses, to min-
imize confusion about where they start and end.

Alternatives are tried from left to right, so the first alternative found for which the entire
expression matches, is the one that is chosen. This means that alternatives are not nec-
essarily greedy. For example: when matching 

against 

"

routine"

, only the

"

rou"

part will match, as that is the first alternative tried, and it successfully match-

es the target string (this might not seem important, but it is important when you are
capturing matched text using parentheses.) Also remember that 

"

|"

is interpreted

as a literal within square brackets, so if you write 

, you're really only

matching 

.

- matches strings 

'

routine'

or 

'

route'

. 

The bracketing construct 

may also be used for define regular subexpres-

sions. Subexpressions are numbered based on the left to right order of their open-
ing parenthesis. First subexpression has number 

matches strings which contain 8, 9 or 10 instances of the 

matches 

'

routi0e', 'routi1e' , 'routine',

'

routinne', 'routinnne'

etc. 

Metacharacters

\1

through

\9

are interpreted as backreferences. 

\

matches pre-

viously matched subexpression 

#

.

matches 

'

aaaa'

and 

'

cc'

. 

matches 

'

abab'

and 

'

123123' 

matches 

"

13"

(in double quotes), or 

'

4'

(in single quotes) or 

(without quotes) etc 

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- SOFTWARE AND HARDWARE SOLUTIONS FOR EMBEDDED WORLD

CHAPTER 2