HP-UX Reference (11i v1 00/12) - 5 Miscellaneous Topics, 7 Device (Special) Files, 9 General Information, Index (vol 9)
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STANDARD Printed by: Nora Chuang [nchuang] STANDARD
/build/1111/BRICK/man5/!!!intro.5
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r
regexp(5) regexp(5)
For example, the ERE abba|cde is interpreted as "match either abba or cde. It does not mean "match
abb followed by a or c followed in turn by de (because concatenation has a higher order of precedence than
alternation).
Expression Anchoring
An ERE can be limited to matching strings that begin or end a line (i.e., anchored) according to the follow-
ing rules:
• A circumflex (ˆ) matches the beginning of a line (anchors the expression to the beginning of a line).
For example, the ERE ˆab matches the string ab in the line abcdef, but not the same string in the
line cdefab.
• A dollar sign ($) matches the end of a line (anchors the expression to the end of a line). For exam-
ple, the ERE ab$ matches the string ab in the line cdefab, but not the same string in the line
abcdef.
• An ERE anchored by both ˆ and $ matches only strings that are lines. For example, the ERE
^abcdef$matches only lines consisting of the string abcdef. Only empty lines match the ERE ˆ$.
The use of duplication characters (+,*) following anchors is illegal.
PATTERN MATCHING NOTATION
The following rules apply to pattern matching notation except as noted in the descriptions of the specific
utilities using pattern matching.
Patterns Matching a Single Character
The following patterns match a single character or a single collating element:
Ordinary Characters
An ordinary character is a pattern that matches itself. An ordinary character is any character in the sup-
ported character set except <newline> and the pattern matching special characters listed in Special Charac-
ters below. Matching is based on the bit pattern used for encoding the character, not on the graphic
representation of the character.
Special Characters
A pattern matching special character preceded by a backslash (\) is a pattern that matches the special
character itself. When not preceded by a backslash, such characters have special meaning in the
specification of patterns. The pattern matching special characters and the contexts in which they have
their special meaning are:
? ∗∗ [ The question mark, asterisk, and left square bracket are special except when used in a
bracket expression (see Pattern Bracket Expression).
Question Mark
A question mark (?),when used outside of a bracket expression, is a pattern that matches any printable or
nonprintable character except <newline>.
Pattern Bracket Expression
The syntax and rules for pattern bracket expressions are the same as for RE bracket expressions found
above with the following exceptions:
The exclamation point character (!) replaces the circumflex character (ˆ) in its role in a non-matching
list in the regular expression notation.
The backslash is used as an escape character within bracket expressions.
Patterns Matching Multiple Characters
The following rules may be used to construct patterns matching multiple characters from patterns match-
ing a single character:
∗∗ The asterisk (∗∗) is a pattern that matches any string, including the null string.
RERE The concatenation of patterns matching a single character is a valid pattern that
matches the concatenation of the single characters or collating elements matched by
each of the concatenated patterns. For example, the pattern a[bc] matches the string
ab and ac.
Section 5−−294 − 6 − HP-UX Release 11i: December 2000
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