如何使用 Linux bash shell 脚本从文件中获取最大数量
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how to get max number from a file with Linux bash shell scripts
提问by Eman
How to get the maximum "rate" and the corresponding "log2c" value from a file as follows? e.g: the max rate is 89.5039 , and log2c 3.0 . thanks a lot.
如何从文件中获取最大“速率”和相应的“log2c”值，如下所示？例如：最大速率是 89.5039 和 log2c 3.0 。多谢。
log2c=5.0 rate=88.7619
log2c=-1.0 rate=86.5412
log2c=11.0 rate=86.1482
log2c=3.0 rate=89.5039
log2c=-3.0 rate=85.5614
log2c=9.0 rate=81.4302
回答by devnull
Use sort:
使用sort：
sort -t= -nr -k3 inputfile | head -1
For the given input, it'd return:
对于给定的输入，它会返回：
log2c=3.0 rate=89.5039
If you want to read the values into variables, you can use the builtin read:
如果要将值读入变量，可以使用内置函数read：
$ IFS=$' =' read -a var <<< $(sort -t= -nr -k3 inputfile | head -1)
$ echo ${var[1]}
3.0
$ echo ${var[3]}
89.5039
回答by Will Vousden
For very large files, using sortwill be quite slow. In this case, it's better to use something like awk, which needs only one pass:
对于非常大的文件，使用sort会很慢。在这种情况下，最好使用像 awk 这样的东西，它只需要一次传递：
$ awk -F= 'BEGIN { max = -inf } { if ( > max) { max = ; line = ##代码## } } END { print line }' test.txt
log2c=3.0 rate=89.5039
The time complexity of this operation is linear, while the space complexity is constant (and small). Explanation:
这个操作的时间复杂度是线性的，而空间复杂度是常数（而且很小）。解释：
awk -F= '...' test.txt: Invoke awk on test.txt, using=as the field separatorBEGIN { max = -inf }: Initialisemaxto something that will always be smaller than whatever you're reading.{ if ($3 > max) { max = $3; line = $0; } }: For each input line, ifmaxis less than the value of the third field ($3), then update it and remember the value of the current line ($0)END { print line }: Finally, print the line we remembered while reading the input.
awk -F= '...' test.txt: 在 test.txt 上调用 awk，=用作字段分隔符BEGIN { max = -inf }：初始化max为始终比您正在阅读的内容小的内容。{ if ($3 > max) { max = $3; line = $0; } }: 对于每一行输入，如果max小于第三个字段的值（$3），则更新并记住当前行的值（$0）END { print line }: 最后，打印我们在读取输入时记住的行。
