My first regular expression

Although famous for a long time, but, after all, is not the opportunity, every time is a shallow, and even did not write a line of regular expression. Today, I finally wrote my first regular expression, remembering:

\s/udisk/[1-9]*

Above this pattern is mainly for, in a long string, find the string "/udkisk/xx", where xx represents a string of numbers, the length of the string is not required.

Explain the above sections:

1) "\s", which represents a white space character, matches any whitespace character, including spaces, tabs, page breaks, and so on. equivalent to [\f\n\r\t\v]. Usually as a starting character for a string. Such characters, in regular expressions called metacharacter, Chinese translation do meta-characters . The metacharacters that represents "one character" are also:

-"\b", which matches the beginning or end of a word in English, can be a space, punctuation, line wrapping. But, in fact, it just matches a position, just to find the beginning or end of a word.

-"." to match any character outside the line break.

-"\d", matching a number. equivalent to [0-9] represented by a set.

-"\w", matching a letter, or number, or underscore, or kanji.

-"Range [1-9]" or "set [FSEFSFD]", in fact both of the corresponding English words can be set, here is the match range, or a character within the collection.

2) So, using the above metacharacters to take my first regular expression apart, is "\s" + "/udisk/" + "[1-9]*", so we want to match the string is "space" + "/udisk/" + "number" + "number" + ... + "Number". The "*" here means that the previous meta-character will appear 0 or more times.

3) The above "*" is called a qualifier , that is, the number of occurrences of the limit. Qualifiers in regular expressions include the following:

-"*", appearing 0 or infinitely multiple times.

-"+", appearing 1 times or infinitely multiple times. At least 1 times.

-"?", appearing 0 or 1 times.

-"{n}", which occurs n times.

-"{n,}", which occurs n or more times.

-"{n,m}", which appears at least n times, up to M times.

4) We can also enclose a string of meta-characters and qualifiers (or other symbols) in parentheses, and then treat the expression as a meta-character, which is called a group. For example, (\w+\.) {2}\w+, which means "xxx.xxx.xxx", where xxx is any number of letters.

This is just a part of the regular expression getting started, so ... and to refuel. In addition, Bash uses the regular expression of the three sharp weapon, also try to master:Grep,sed,awk.

My first regular expression