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HandBooks Professional Java-C-Scrip-SQL part 222

Tham khảo tài liệu 'handbooks professional java-c-scrip-sql part 222', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 1.11 Shell Tools awk sed and egrep are a related set of Unix shell tools for text processing. awk and egrep use a DFA match engine and sed uses an NFA engine. For an explanation of the rules behind these engines see Section 1.2. This reference covers GNU egrep 2.4.2 a program for searching lines of text GNU sed 3.02 a tool for scripting editing commands and GNU awk 3.1 a programming language for text processing. 1.11.1 Supported Metacharacters awk egrep and sed support the metacharacters and metasequences listed in Table 1-46 through Table 1-50. For expanded definitions of each metacharacter see Section 1.2.1. Table 1-46. Character representations Sequence Meaning Tool a Alert bell . awk sed b Backspace supported only in character class. awk f Form feed. awk sed n Newline line feed . awk sed r Carriage return. awk sed t Horizontal tab. awk sed v Vertical tab. awk sed ooctal A character specified by a one- two- or three-digit octal code. sed octal A character specified by a one- two- or three-digit octal code. awk xhex A character specified by a two-digit hexadecimal code. awk sed ddecimal A character specified by a one two or three decimal code. awk sed cchar A named control character e.g. cC is Control-C . awk sed b Backspace. awk metacharacter Escape the metacharacter so that it literally represents itself. awk sed egrep Table 1-47. Character classes and class-like constructs Class Meaning Tool . Matches any single character listed or contained within a listed range. awk sed egrep r. Matches any single character that is not listed or contained within a listed range. awk sed egrep . Matches any single character except newline. awk sed egrep w Matches an ASCII word character a - zA- Z0-9_ . egrep sed W Matches a character that is not an ASCII word character Aa- zA- Z0-9_ . egrep sed prop Matches any character in the POSIX character class. awk sed A prop Matches any character not in the POSIX character class. awk sed Table 1-48. Anchors and other zero-width .