Ben Chuanlong Du's Blog

And let it direct your passion with reason.

Regular Expression Equivalent

  1. The order of precedence of operators in POSIX extended regular expression is as follows.

    1. Collation-related bracket symbols [==], [::], [..]
    2. Escaped characters \
    3. Character set (bracket expression) []
    4. Grouping ()
    5. Single-character-ERE duplication *, +, ?, {m,n}
    6. Concatenation
    7. Anchoring ^, $
    8. Alternation |

  2. Some regular expression patterns are defined using a single leading backslash, e.g., \s, \b, etc. However, since special …

Regular Expression in Bash

It is suggested that you use Python script instead of Shell script as much as possible. If you do have to stick with Shell script, you can use =~ for regular expression matching in Bash. This make Bash syntax extremely flexible and powerful. For example, you can match multiple strings using …

Regular Expression in Python

Online Regular Expression Tester

  1. The Python module re automatically compiles a plain/text pattern using re.compile and caches it, so there's not much benefit to compile plain/text patterns by yourself.

  2. Some regular expression patterns are defined using a single leading backslash, e.g., \s, \b, etc. However, since special characters (e.g., \) need to be escaped in strings in most programming languages, you will need the string "\\s"