tcl的正则表达式命令regexp的参数-lineanchor的理解

tcl中正则表达式用得很多，往往一句代码能够做好几条其他语句才能做完的工作，高效快捷；

在处理string中逐行匹配的情况下往往是用参数-line，但其实-line相当于-lineanchor和-linestop。

在使用-lineanchor时的实践：

-lineanchor

Changes the behavior of “^” and “$” (the “anchors”) so they match the beginning and end of a line respectively. This is the same as specifying the
(?w) embedded option (see the re_syntax manual page).

ex.

% set dataRtn {Select the version of EVDEV to use

> 1. Enable EVDEV 1.0.0.0 (EVDEV_1_0_0_0)

2. Disable EVDEV (NO_EVDEV)

choice[1-2]:

*

* EVDEV Menu

*

Select the version of EVDEV_DEMO to use

> 1. Enable EVDEV_DEMO 1.0.0.0 (EVDEV_1_0_0_0_DEMO_1_0_0_0)

2. Disable EVDEV_DEMO (NO_EVDEV_DEMO)

choice[1-2]:

Select the version of EVDEV_DRV to use

> 1. Enable EVDEV_DRV 1.0.0.0 (EVDEV_1_0_0_0_DRV_1_0_0_0)

2. Disable EVDEV_DRV (NO_EVDEV_DRV)

choice[1-2]:}

我想将上面变量dataRtn中的以*开头的所有行删除。

最开始认为参数-lineanchor会匹配到每行的开头和结尾，不会存在贪婪匹配的问题：

% regsub -all -lineanchor {^\*.*$} $dataRtn {} dataRtn1

% set dataRtn1

Select the version of EVDEV to use

> 1. Enable EVDEV 1.0.0.0 (EVDEV_1_0_0_0)

2. Disable EVDEV (NO_EVDEV)

choice[1-2]:

%

发现错了，虽然参数-lineanchor会让^和$ 匹配行首和行尾，但是照样是贪婪匹配。最后的$ 会一直匹配到整个string的结尾。

于是使用下面的命令：

% regsub -all -lineanchor {^\*.*?$} $dataRtn {} dataRtn1

% set dataRtn1

Select the version of EVDEV to use

> 1. Enable EVDEV 1.0.0.0 (EVDEV_1_0_0_0)

2. Disable EVDEV (NO_EVDEV)

choice[1-2]:

---------------------------->这里是空行

---------------------------->这里是空行

---------------------------->这里是空行

Select the version of EVDEV_DEMO to use

> 1. Enable EVDEV_DEMO 1.0.0.0 (EVDEV_1_0_0_0_DEMO_1_0_0_0)

2. Disable EVDEV_DEMO (NO_EVDEV_DEMO)

choice[1-2]:

Select the version of EVDEV_DRV to use

> 1. Enable EVDEV_DRV 1.0.0.0 (EVDEV_1_0_0_0_DRV_1_0_0_0)

2. Disable EVDEV_DRV (NO_EVDEV_DRV)

choice[1-2]:

期望把空行也删除。

% regsub -all -lineanchor {^\*.*?\n$} $dataRtn {} dataRtn1

% set dataRtn1

Select the version of EVDEV to use

> 1. Enable EVDEV 1.0.0.0 (EVDEV_1_0_0_0)

2. Disable EVDEV (NO_EVDEV)

choice[1-2]:

显然不行，虽然$会匹配到行尾，但是似乎回车换行(\n)不是每行的结尾，所以匹配失败，导致一直匹配到string的末尾；

% regsub -all -lineanchor {^\*.*?\n} $dataRtn {} dataRtn1

% set dataRtn1

Select the version of EVDEV to use

> 1. Enable EVDEV 1.0.0.0 (EVDEV_1_0_0_0)

2. Disable EVDEV (NO_EVDEV)

choice[1-2]:

Select the version of EVDEV_DEMO to use

> 1. Enable EVDEV_DEMO 1.0.0.0 (EVDEV_1_0_0_0_DEMO_1_0_0_0)

2. Disable EVDEV_DEMO (NO_EVDEV_DEMO)

choice[1-2]:

Select the version of EVDEV_DRV to use

> 1. Enable EVDEV_DRV 1.0.0.0 (EVDEV_1_0_0_0_DRV_1_0_0_0)

2. Disable EVDEV_DRV (NO_EVDEV_DRV)

choice[1-2]:

这就是想要的结果了——不把\n当作结尾。