三个 awk 调用合二为一

Question

以下内容按预期工作：

awk '$1 <= -700 { print $3 }' FS="," tmp | awk '!seen[$0]++'

23
60
73
91

现在我计算这四个值并打印数字 4：

awk '$1 <= -700 { print $3 }' FS="," tmp | awk '!seen[$0]++' | awk '{ count++ } END { print count }'

4

有没有一种更短的方法可以在一次调用中执行这三个 awk 调用？

非常感谢提示，

Answer 1

像这样：

awk '$1 <= -700 && !seen[$3]++ {c++} END{print c+0}' FS="," tmp

解释：

# If column 1 <= -700 and we've not seen the value of column 3 yet ...
$1 <= -700 && !seen[$3]++ {
   # ... increment the counter c
   c++
}

# When the end of the input file is reached, print the counter
END {
    # Note: incrementing the counter by 0 ensures that c
    # has the value 0 when no line matched the criterias and thereby
    # c has never been incremented. Without this, c would be an
    # empty string. This gets often forgotten. Thanks @Ed Morton!

    # Alternatively you may run the program as awk -v c=0 ...
    print c+0 
}