linux - 从文件中读取模式，grep 仅第一次出现

Question

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Answer 1

一个使用 awk:

$ awk 'NR==FNR{a[$1]=1;next}a[$2]==1{print $2;a[$2]++}' pattern sample
Pattern1
Pattern2
Pattern3

解释:

$ awk '           # well, awk
NR==FNR {         # for the first file
    a[$1]=1       # hash each keyword and set it as 1
    next          # next record
}
a[$2]==1 {        # second file, if the word in 2nd column was hashed and 1
    print $2      # output it
    a[$2]++       # and increase its value above 1
}' pattern sample # mind the order