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From: Matthew Carter <m@ahungry.com>
Newsgroups: comp.lang.php
Subject: Re: Run AWK using shell_exec
Date: Fri, 27 Feb 2015 00:28:52 -0500
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"Dan'l B" <dan.hinckley@gmail.com> writes:

> On Thursday, February 26, 2015 at 9:23:19 PM UTC-5, Ben Bacarisse wrote:
>> "Dan'l B" <> writes:
>> <snip>
>> > Substituting a variable containing a path-to-the file, I can't seem to
>> > get the escaping right:
>> >
>> > Works:
>> > $maxLow = shell_exec("/usr/bin/awk 'min==\"\" || $4~/^[^[:alpha:]]+$/
>> > && $4 < min {min=$4} END{print min}' fullyear.txt");
>> >
>> > Fails: (where $tidesFilePath is an absolute path to the fullyear.txt file).
>> > $tidesFilePath = "/Tidefiles/fullyear.txt"; (example path)
>> > $maxLow = shell_exec("/usr/bin/awk 'min==\"\" || $4~/^[^[:alpha:]]+$/
>> > && $4 < min {min=$4} END{print min}'" . $tidesFilePath . \"");
>> 
>> That's not syntactically correct PHP.  I'm not sure what the . \"" bit
>> at the end is supposed to do, but you don't need it.  You *do* need a
>> space between the end of the awk script in single quotes and the file
>> name:
>> 
>>  ... $4 < min {min=$4} END{print min}' " . $tidesFilePath);
>> 
>> But you should be very careful when including variables into a shell
>> command.  Never forget little Bobby Tables http://www.xkcd.com/327/
>> 
> Thanks, still doesn't seem to work but I'll double-check the path. I
> do grasp the problem of variables in shell commands but is there an
> alternative way to get the highest and lowest values in a column of
> text in a multi-column text file using only PHP?

This works on your sample data:

<?php

$data = array_filter (array_map (
  function ($l)
  {
    return explode (' ', preg_replace ('/\s+/', ' ', $l))[3];
  }, explode ("\n", file_get_contents ('/tmp/hi-low'))), 'is_numeric');

sort ($data); 

$d1 = $d2 = $data; // This is done incase there is only one entry

$low = array_shift ($d1);
$hi  = array_pop ($d2);

var_dump ($low, $hi);

Fine tune as needed of course (this assumes one or more whitespace such
as tab or space breaks the 'columns').  You'd probably want your data to
stick to a real column format, such as CSV or TSV though.

-- 
Matthew Carter (m@ahungry.com)
http://ahungry.com