bash中的=〜运算符支持哪种正则表达式语法? [英] What regex syntax is supported by the =~ operator in bash?

问题描述

我发现我可以在我的4.2.10(1)BASH中使用 =~ 运算符代替 expr 命令. (在命令内)它比expr快得多，并且在循环较大的循环内部，这一事实可能很重要.

I discovered that I can use =~ operator instead of expr command in my 4.2.10(1) BASH. It is much faster (within a command) than expr and this fact could be important inside in a loop with large repetition.

我能够使用大多数正则表达式的元字符，但不是全部.

I was able to use most of the meta characters of regular expression but not all.

例如，我可以检查一个字符串是否完全匹配3个重复(一个小写字母，一个数字，一个点):

For example I can check a string matches exactly 3 repetitions of (one small letter, one digit, one dot):

[[ "b3.f5.h3." =~ ^([a-z][0-9]\.){3}$  ]] && echo OK
OK

然后我可以选择匹配的子字符串:

and I can select matched substrings:

[[ "whatis12345thetwo765nmbers" =~ ^[a-z]+([0-9]+)[a-z]+([0-9]+) ]] && \
echo "The two number fields are: ${BASH_REMATCH[1]}  ${BASH_REMATCH[2]}"
The two number fields are: 12345  765

但是我想使用更多的元字符，例如

But I would like to use more meta characters, such as the ones listed on this TLDP page.

我特别想匹配单词边界: \b ， \B ， \< ， .

I would especially like to match word boundaries: \b, \B, \<, \> .

我试图在高级Bash脚本指南(第18和37章)中找到答案，但是没有成功.

I tried to find an answer in the Advanced Bash-Scripting Guide (in Chapters 18 and 37) but was unsuccessful.

在哪里可以找到 =~ 运算符的详细说明?

Where can I find a detailed description of =~ operator?

目前，我只对BASH感兴趣，而对gawk，sed，perl或其他工具不感兴趣.

At the moment I am interested only in BASH and not in gawk, sed, perl or other tools.

推荐答案

=~支持POSIX ERE，除了本地C库添加的扩展名外，没有其他扩展名(从字面上讲，它调用标准C库的regex调用).因此，关于保证可支持的功能的规范文档(与本地C库可能另外添加的可选功能相对)是ERE上的规范，

=~ supports POSIX ERE with no extensions additional to those added by the local C library (literally, it calls the standard C library's regex calls). Thus, the canonical documentation on features it's guaranteed to support (as opposed to optional features your local C library may add in addition) is the specification on ERE, IEEE 1003.1, section 9.4.

对此进行放大:由一个特定的libc(例如glibc)添加但POSIX规范中不存在的任何内容(例如\<)不能期望bash支持的所有平台都可以移植

To amplify this: Anything, such as \<, added by one particular libc (ie. glibc) but not present in the POSIX specification cannot be expected to work portably across all platforms bash supports.

POSIX指定的特殊字符(如9.4.3节中所述，如 )不包括 <，>，b或B；这些都是GNU扩展，不可移植.

The POSIX-specified special characters (as given in section 9.4.3 of the standard) do not include <, >, b or B; these are all GNU extensions and nonportable.

这篇关于bash中的=〜运算符支持哪种正则表达式语法?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！