20. Regular Expression Fundamentals（正则表达式基础）
- Beginning of line (
^) - End of line (
$) - Single Character (.)
- Zero or more Occurrences (
*) - One or more Occurrence (
+) - Zero or one Occurrence (
?) - Escaping the Special Character (
) - Character Class (
[0-9])
21. Additional Regular Expressions （扩展正则表达式）
- OR Operation (
|) - Exactly M Occurrences (
{m}) - M to N Occurrences (
{m,n}) - Word Boundary (
b)（单词边界符） - Back References (
n)（反向引用，n为数字）
22. Sed Substitution Using Regular Expression
Convert the DOS file format to Unix file format using sed:
使用
sed将DOS下的新行换行符(CR/LF)替换成Unix下的格式1sed 's/.$//' filename
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