Santiago - Find the secret combination

#bash #find #grep #cut
Type: Do
Description: Alice the spy has hidden a secret number combination, find it using these instructions:

1. Find the number of lines with occurrences of the string Alice (case sensitive) in the *.txt files in the /home/admin directory
2. There's a file where Alice appears exactly once. In that file, in the line after that "Alice" occurrence there's a number.
   Write both numbers consecutively as one (no new line or spaces) to the solution file. For example if the first number from 1) is 11 and the second 22, you can do echo -n 11 > /home/admin/solution; echo 22 >> /home/admin/solution or echo "1122" > /home/admin/solution.

Test: Running md5sum /home/admin/solution returns d80e026d18a57b56bddf1d99a8a491f9(just a way to verify the solution without giving it away.)

Notes and solution:

First, we list all the files on the /home/admin/ directory.
ls /home/admin/

There are one directory and one file that shouldn't be taken into consideration when counting the number of times Alice appears, so we filter those two with find.

find /home/admin/ -maxdepth 1 -iname "*.txt"

where -maxdepth 1 ensures that we only search in the current directory (therefore filtering any files that may be in the unwanted sub directory) and -iname "*.txt" ensures we only see text files.

Now, we have to search for the word Alice in the files and count how many times it appears. Both of these things can be accomplished with grep -c.

find /home/admin/ -maxdepth 1 -iname "*.txt" | xargs grep -c 'Alice'

where xargs passes the output of the .txt file search results to the grep command as arguments, where they scanned for the word Alice and then the flag -c makes the command count how many times it found the word.

Now, we filter only the word count of each file with cut

find /home/admin/ -maxdepth 1 -iname "*.txt" | xargs grep -c 'Alice' | cut --delimiter ":" --fields 2

where we use : as a --delimiter to separate each line in two and then we choose the second --fields.

To sum this numbers, we'll first paste all of them in a single line with a plus sign in between them.

find /home/admin/ -maxdepth 1 -iname "*.txt" | xargs grep -c 'Alice' | cut --delimiter ":" --fields 2 | paste -sd+ -

Finally, we give that output to the bc command to interpret and sum.

find /home/admin/ -maxdepth 1 -iname "*.txt" | xargs grep -c 'Alice' | cut --delimiter ":" --fields 2 | paste -sd+ - | bc

There are 414 mentions of Alice in total.
The .text file that contains exactly one mention of Alice is 1342-0.txt.

With this information, we conclude that the answers is 4141342.