从一个文件中读取字符串，grep另一个文件中的第一个匹配项 [英] Read string from one file, grep the first occurrence in another file

问题描述

我正在从文件devices_list.txt中读取一个字符串.

I'm reading a string from file, appliances_list.txt.

appliances_list.txt包含

appliances_list.txt contains

fridge
dryer
ironbox
microwave 

我正在读取的文件是myappliances.txt.内容是

The file I'm reading is myappliances.txt. Content is

I have a fridge
I have another fridge
I have a refridgerator
I have a microwave
I have ironbox at home
I have another microwave
I have a hairdryer

我正在使用

grep -o -m1 -f appliances_list.txt myappliances.txt

输出为

fridge

我想要的输出是每个字符串的第一次出现(完全匹配)

My desired output is, first occurrence of each string (exact match)

fridge
microwave
ironbox

有人可以指出我正确的方向吗?

Can someone point me in the right direction?

推荐答案

$ cat tst.awk
NR==FNR { strings[$0]; ++numStrings; next }
{
    for (i=1;i<=NF;i++) {
        if ($i in strings) {
            print $i
            delete strings[$i]
            if (--numStrings == 0) {
                exit
            }
            break
        }
    }
}

$ awk -f tst.awk appliances_list.txt myappliances.txt
fridge
microwave
ironbox

这将非常有效，因为它会从找到的字符串列表中删除每个找到的字符串，因此每一行的比较需要的次数更少，并且当列表中没有更多的字符串时将退出程序，因此不会浪费程序时间读取第二个文件的其余行.

That will be very efficient since it will remove each found string from the list of strings as it's found so there's fewer comparisons necessary on every line and when there's no more strings in the list will exit the program so it doesn't waste time reading the remaining lines of the 2nd file.

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