regex - awk 和 regex 的简单问题

Question

 echo xx y11y rrr | awk '{ if ($2 ~/y[1-5]{2}y/) print $3}'

为什么我无法获得任何输出？

谢谢你。

Answer 1

您需要通过指定 --posix 在正则表达式匹配中启用“间隔表达式”。或 --re-interval选项。

例如

echo xx y11y rrr | awk --re-interval '{ if ($2 ~ /y[1-5]{2}y/) print $3}

从手册页:

--re-interval Enable the use of interval expressions in regular expression matching (see Regular Expressions, below). Interval expressions were not traditionally available in the AWK language. The POSIX standard added them, to make awk and egrep consistent with each other. However, their use is likely to break old AWK programs, so gawk only provides them if they are requested with this option, or when --posix is specified.