bash 在Unix中提取变量中两个字符串之间的部分
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Extract part between two strings in a variable in Unix
提问by Noobie
I have a string,
我有一根绳子，
tester_one="update set_tables set abc=7 where bcd=9"
Here I wish to extract only the part between "set" and "where",
这里我只想提取“set”和“where”之间的部分，
abc=7
I tried a couple of Unix commands, but it picked up any occurrences of setor where encountered, before the part where I want it to pick up.
我尝试了几个 Unix 命令，但它在我希望它选择的部分之前选择了任何出现的set或遇到的地方。
I have an idea on how to do it Java but I am lost in Unix as I am new to this.
我对如何使用 Java 有一个想法，但我在 Unix 中迷失了方向，因为我是新手。
采纳答案by viraptor
You can get it out with sed. Something like:
你可以用 sed 把它弄出来。就像是：
echo "$tester_one" | sed 's/.* set \(.*\) where .*//'
回答by John1024
Using sed
使用 sed
$ echo "$tester_one" | sed -E 's/.*set (.*) where.*//'
abc=7
To capture it in a variable:
要在变量中捕获它：
$ new=$(echo "$tester_one" | sed -E 's/.*set (.*) where.*//')
$ echo $new
abc=7
Using awk
使用 awk
$ echo "$tester_one" | awk '{sub(/.*set /,""); sub(/ where.*/,""); print;}'
abc=7
Using grep -P
使用 grep -P
If your grep supports the -P(perl-like) option:
如果您的 grep 支持-P(perl-like) 选项：
$ echo "$tester_one" | grep -oP '(?<=set ).*(?= where)'
abc=7
回答by Jahid
Using Bash Pattern Matching:
使用Bash 模式匹配：
#!/bin/bash
tester_one="update set_tables set abc=7 where bcd=9"
pat=".* set (.*) where"
[[ $tester_one =~ $pat ]]
echo "${BASH_REMATCH[1]}"
回答by fedorqui 'SO stop harming'
You can also use setand whereas field separators and print the field that lies in between them:
您还可以使用set和where作为字段分隔符并打印位于它们之间的字段：
$ awk -F"set | where" '{print }' <<< "update set_tables set abc=7 where bcd=9"
abc=7
回答by ghoti
As with your other question, this can be achieved in pure bash, without the use of external tools like sed/awk/grep.
与您的其他问题一样，这可以在纯 bash 中实现，而无需使用 sed/awk/grep 等外部工具。
#!/usr/bin/env bash
tester_one="update set_tables set abc=7 where bcd=9"
output="${tester_one#* set }"
output="${output% where }"
echo "$output"
Note the spaces around "set" and "where" in the parameter expansion lines. As you might expect, you'll need to be careful with this if the $tester_onevariable contains the distinct "set" or "where" in places that you don't expect them.
注意参数扩展行中“set”和“where”周围的空格。如您所料，如果$tester_one变量在您不希望它们的地方包含不同的“set”或“where”，则需要小心处理。
That said, I like Jahid's answerbetter. :-)
也就是说，我更喜欢贾希德的回答。:-)
