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2

extract text from a file using terminal?

rated 0 times [ 2] [ 0] / answers: 1 / hits: 5923 / 3 Years ago, sun, may 16, 2021, 10:18:43

I want to process the body of text and extract an integer from a specific position in the text, but I'm not sure how to describe that 'particular position'. Regular expressions really confuse me. I spent (wasted) a couple hours reading tutorials and I feel no closer to an answer :(

There's a bunch of text which may or may not include integers (that I don't want) and then there's a line that always contains

id_ad=1929170&action

and then followed by a bunch of garbage I don't care about, again it may or may not include one or more integers.

So intuitively I know I just want to ignore everything up to (and including) id_ad= and ignore everything after (and including) &action and I'll be left with the integer I want. And I know I can use regular expressions to achieve this. But I can't seem to figure it out.

I'd like to do this as a one liner from terminal if possible.

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rontablis

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3 Years ago

answered 3 Years ago montwim · Accepted Answer

Not so much a one liner (although the command to run it is a one liner :) ), but here is a python option:

#!/usr/bin/env python3

import sys

file = sys.argv[1]



with open(file) as src:

    text = src.read()



starters = [(i+6, text[i:].find("&action")+i) for i in range(len(text)) if text[i:i+6] == "id_ad="]

if len (starters) > 0:

    for item in starters:

        print(text[item[0]:item[1]])

The script first lists all occurrences (indexes) of the (start) string "id_ad=", in combination with (end) string "&action". Then it prints all that is between those "markers".

Extracted from a prepared file:

" I want to process the body of text and extract an integer from a specific position in the text, but I'm not sure how to describe that 'particular position'. Regular expressions really confuse me. I spent (wasted) a couple hours reading tutorials and I feel no closer to an answer :(
There's a bunch of text which may or may not include integers (that I don't want) and then there's a line that always contains
id_ad=1929170&action
There's a bunch of text which may or may not include integers (that I don't want) and then there's a line that always contains
id_ad=1889170&action and then followed by a bunch of garbage I don't care about, again it may or may not include one or more integers.
There's a bunch of text which may or may not include integers (that I don't want) and then there's a line that always contains id_ad=1889170&action and then followed by a bunch of garbage I don't care about, again it may or may not include one or more integers.
There's a bunch of text which may or may not include integers (that I don't want) and then there's a line that always contains id_ad=1929990&action"

The result is:

How to use

Paste the script into an empty file, save it as extract.py run it by the command:

python3 <script> <file>

Note

If there is only one occurrence in the text file, the script can be much shorter:

#!/usr/bin/env python3

import sys

file = sys.argv[1]



with open(file) as src:

    text = src.read()

print(text[text.find("id_ad=")+6:text.find("&action")])