regex - 正则表达式用已知的第一个和最后一个单词替换子字符串

Question

我有一个字符串说"xyz walked his dog abc"。我想删除子字符串"walked his dog"，只拥有"xyz abc". 我怎样才能在 bash 正则表达式中这样做？

Answer 1

纯重击：

var="xyz walked his dog abc"
echo ${var/walked*dog/}
xyz  abc

Answer 2

你可以使用一个数组：

string="xyz walked his dog abc"

a=( $string )

result="${a[0]} ${a[-1]}"

Answer 3

虽然对于这个特定的操作来说正则表达式是多余的（我推荐ravoori's answer），但如果需要更改，最好了解语法：

# Two capture groups, one preceding the string to remove, the other following it
regex='(.*)walked his dog(.*)'
[[ $string =~ $regex ]]
# Elements 1 through n of BASH_REMATCH correspond to the 1st through nth capture
# groups. (Element 0 is the string matched by the entire regex)
string="${BASH_REMATCH[1]}${BASH_REMATCH[2]}"

Answer 4

最简单的方法可能是使用sed：（sed -r 's/walked his dog//'用空字符串替换子字符串）。或者使用内置的替换机制（但不支持正则表达式）：a="xyz walked his dog abc"; echo "${a/walked his dog/}"