Shell script: find maximum value in a sequence of integers without sorting

shell, unix

Solution

You can use this if no negative number is expected:

awk '$0>x{x=$0};END{print x}' input.txt

Use this to support negative numbers:

awk 'BEGIN{x=-2147483648};$0>x{x=$0};END{print x}' input.txt

Initializing `x` allows the solution to properly handle integer lists with values <= 0. See the comments for more details.

Problem

I have a file with a long list of integers: ``` 10 4 66 .... ``` I want to find the maximum value using UNIX command line tools. I know I can use `sort` (and indeed there are solutions to this problem on SO that use `sort`), but that's inefficient, requiring O(N*log(N)) and plenty of memory. With a simple for loop, I should be able to find the maximum value in O(N) and a couple of bytes of memory. It seems there must be some program out there (with a name like `max`) that does this out of the box---is that true?

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