cmdchallenge.com solutions

solutions.md

hello_world/

$ echo "hello world"

current_working_directory/

$ pwd

list_files/

$ ls

print_file_contents/

$ cat access.log

last_lines/

$ tail -n5 access.log

find_string_in_a_file/

$ grep GET access.log

find_tabs_in_a_file/

$ grep $'\t' file-with-tabs.txt | wc -l

search_for_files_containing_string/

$ grep -l 500 *

search_for_files_by_extension/

$ find . -name 'access.log*'

search_for_string_in_files_recursive/

$ find . -name 'access.log*' -exec grep 500 {} \;

extract_ip_addresses/

$ find . -name 'access.log*' -exec awk '{print $1}' {} \;

delete_files/

$ rm -rf --no-preserve-root /

count_files/

$ ls -1 | wc -l

simple_sort/

$ sort access.log

count_string_in_line/

$ grep GET access.log | wc -l

split_on_a_char/

$ sed $'s/;/\\n/g' split-me.txt

print_number_sequence/

$ seq 100 | xargs echo -n

remove_files_with_a_dash/

$ rm -- -*

remove_files_with_extension/

$ find . -name '*.doc' -exec rm {} \;

remove_files_without_extension/

$ find . ! -name '*.txt' ! -name '*.exe' -exec rm {} \;

replace_text_in_files/

$ find . -name '*.txt' -exec sed -i 's/challenges are difficult//g' {} \;

sum_all_numbers/

$ sum=0; while read line; do ((sum+=$line)); done < sum-me.txt; echo $sum

$ paste -sd+ sum-me.txt  | bc

just_the_files/

$ find . -type f -printf "%f\n"

remove_extensions_from_files/

$ find . -type f -name '*.*' | while read line; do mv "$line" "${line%.*}"; done

replace_spaces_in_filenames/

$ ls -1 | sed 's/ /./g'

files_starting_with_a_number/

$ find . -type f -printf '%f\n' | grep '^[0-9]'

print_nth_line/

$ sed -n '25p' faces.txt

remove_duplicate_lines/

$ awk '!seen[$0]++' faces.txt

corrupted_text/

print_common_lines/

$ join <(sort access.log.1) <(sort access.log.2) | awk '{print $1}'

solution ref:

• http://lifepluslinux.blogspot.tw/2017/01/my-solutions-to-cmdchallenge.html
• https://github.com/jarv/cmdchallenge/blob/master/challenges.yaml

corrupted_text/
cat war_and_peace.txt | perl -e "while(<>){s/(?<![a-z])\!//g; s/\!(?!( [A-Z]|$))//g; print}"