Get substring between two markers in a specific line of a file

Question

I'm trying to select a specific section of a specific line within a file.

For instance, I want to isolate the first line of text from a file and get the numeric value of rate without the trailing kbit text.

Sample file contents:

tc class add dev br-lan parent 1:1 classid 1:2 htb rate 100kbit ceil 100kbit
tc class add dev br-lan parent 1:1 classid 1:3 htb rate 200kbit ceil 200kbit
tc class add dev br-lan parent 1:1 classid 1:4 htb rate 300kbit ceil 300kbit

I would like to select the data between "rate " (notice the space after rate) and "kbit" based on the line number, then store it as a variable.

Expected Result:

Effectively, I would like to retrieve the results based on, for example; line 1:

100

Then store this value as a variable.

This won't work with substr, as shown here: http://php.net/manual/en/function.substr.php as the length of the integer retrieved may not always be the same length.

File path:

../etc/init.d/bandwidthlimiters/rulestest

Answer 1

Try this hope it will work fine.

<?php
ini_set('display_errors', 1);

$lines=file("path/of/file.txt");//get the content of file as an array of lines
$result=array();
foreach($lines as $lineNo=>$line)
{
    preg_match('/rate\s*\K[\d]+/', $line,$matches);
    $result[$lineNo+1]=$matches[0];
}
print_r($result);

Answer 2

<?php

$output_arr=array();
$handle = fopen("inputfile.txt", "r");
if ($handle) {

    $i=1;
    while (($line = fgets($handle)) !== false) {

    $test_string=$line;
    $test_string=str_replace(" htb rate ","@@",$test_string);
    $test_string=str_replace("kbit ceil ","@@",$test_string);

    $tmp = explode("@@", $test_string);
    array_push($output_arr,$tmp[1]);
    $i++;
   }

    fclose($handle);
} else {
    // error opening the file.
} 

echo $output_arr[2]

?>

Answer 3

This task requires two basic subtasks:

1. Accessing a specified line in a file and
2. Extracting a substring from a string.

For subtask #1, there is good advice at PHP: Read Specific Line From File which explains that a developer can choose succinct syntax with file() to read relatively small files or use an SplFileObject with seek() to efficiently target one line.

1. With file():

   $lineNumber = 1;
   $line = file('your/path/to/file.txt')[$lineNumber - 1];
   

2. With SplFileObject:

   $lineNumber = 1;
   $spl = new SplFileObject('your/path/to/file.txt'); // temporarily locks file
   $line = $spl->seek($lineNumber - 1)->current();
   $spl = null; // unlock file
   

For subtask #2, targetting the desired substring can be done a myriad of ways depending on the sought characters, preceeding characters, delimiters in the text, etc. I'll list a couple basic techniques.

1. Explode on delimiting spaces and cast as an integer to trim kbit characters by consequence: Demo

   $rate = (int) explode(' ', $line)[11];
   

2. Regular expression: Demo

   $rate = preg_replace('/.* rate (\d+).*/', '$1', $line);
   

No matter which combination of techniques you choose, there is certainly no need to implement hacky string replacements to introduce placeholders before extracting the desired text.

Answer 4

This should solve the issue:

<?php
$lines = file("../etc/init.d/bandwidthlimiters/rulestest");
$results = array();
foreach($lines as $num=>$line) {
    preg_match("/([0-9]+)\s*kbit/i", $str, $out);
    if(isset($out[1])) $results[$num] = $out[1];
}

Now,

$results = array with results where index is the line number corresponding each result

Answer 5

Verifies there's a ("rate ") string before and ("kbit") string ahead, not consuming either of them:

/(?<=rate\s)\d+(?=kbit)/

Code:

<?php
$lines=file("file.txt");
$result=array();
foreach($lines as $oneline)
{
    preg_match('/(?<=rate\s)\d+(?=kbit)/', $oneline, $matches);
    $result[]=$matches[0];
}
?>

file.txt:

tc class add dev br-lan parent 1:1 classid 1:2 htb rate 100kbit ceil 100kbit
tc class add dev br-lan parent 1:1 classid 1:3 htb rate 200kbit ceil 200kbit
tc class add dev br-lan parent 1:1 classid 1:4 htb rate 300kbit ceil 300kbit

$result:

Array
(
    [0] => 100
    [1] => 200
    [2] => 300
)