tcl的正則表示式命令regexp的引數-lineanchor的理解
tcl中正則表示式用得很多，往往一句程式碼能夠做好幾條其他語句才能做完的工作，高效快捷；
在處理string中逐行匹配的情況下往往是用引數-line，但其實-line相當於-lineanchor和-linestop。
在使用-lineanchor時的實踐：
Changes the behavior of “^” and “$” (the “anchors”) so they match the beginning and end of a line respectively. This is the same as specifying the (?w) embedded option (see the manual page).
ex.
% set dataRtn {Select the version of EVDEV to use
> 1. Enable EVDEV 1.0.0.0 (EVDEV_1_0_0_0)
2. Disable EVDEV (NO_EVDEV)
choice[1-2]:
*
* EVDEV Menu
*
Select the version of EVDEV_DEMO to use
> 1. Enable EVDEV_DEMO 1.0.0.0 (EVDEV_1_0_0_0_DEMO_1_0_0_0)
2. Disable EVDEV_DEMO (NO_EVDEV_DEMO)
choice[1-2]:
Select the version of EVDEV_DRV to use
> 1. Enable EVDEV_DRV 1.0.0.0 (EVDEV_1_0_0_0_DRV_1_0_0_0)
2. Disable EVDEV_DRV (NO_EVDEV_DRV)
choice[1-2]:
我想將上面變數dataRtn中的以*開頭的所有行刪除。
最開始認為引數-lineanchor會匹配到每行的開頭和結尾，不會存在貪婪匹配的問題：
% regsub -all -lineanchor {^\*.*$} $dataRtn {} dataRtn1
% set dataRtn1
Select the version of EVDEV to use
> 1. Enable EVDEV 1.0.0.0 (EVDEV_1_0_0_0)
2. Disable EVDEV (NO_EVDEV)
choice[1-2]:
%
發現錯了，雖然引數-lineanchor會讓^和$ 匹配行首和行尾，但是照樣是貪婪匹配。最後的$ 會一直匹配到整個string的結尾。
於是使用下面的命令：
% regsub -all -lineanchor {^\*.*?$} $dataRtn {} dataRtn1
% set dataRtn1
Select the version of EVDEV to use
> 1. Enable EVDEV 1.0.0.0 (EVDEV_1_0_0_0)
2. Disable EVDEV (NO_EVDEV)
choice[1-2]:
---------------------------->這裡是空行
---------------------------->這裡是空行
---------------------------->這裡是空行
Select the version of EVDEV_DEMO to use
> 1. Enable EVDEV_DEMO 1.0.0.0 (EVDEV_1_0_0_0_DEMO_1_0_0_0)
2. Disable EVDEV_DEMO (NO_EVDEV_DEMO)
choice[1-2]:
Select the version of EVDEV_DRV to use
> 1. Enable EVDEV_DRV 1.0.0.0 (EVDEV_1_0_0_0_DRV_1_0_0_0)
2. Disable EVDEV_DRV (NO_EVDEV_DRV)
choice[1-2]:
期望把空行也刪除。
% regsub -all -lineanchor {^\*.*?\n$} $dataRtn {} dataRtn1
% set dataRtn1
Select the version of EVDEV to use
> 1. Enable EVDEV 1.0.0.0 (EVDEV_1_0_0_0)
2. Disable EVDEV (NO_EVDEV)
choice[1-2]:
顯然不行，雖然$會匹配到行尾，但是似乎回車換行(\n)不是每行的結尾，所以匹配失敗，導致一直匹配到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]:
這就是想要的結果了——不把\n當作結尾。