Saturday, 28 January 2017

My solutions to cmdchallenge

I recently stumbled upon https://cmdchallenge.com which sort of tests your command line knowledge and comfortability. You have to basically solve all the challenges in a single line of bash. It is pretty simple and fun. You should give it a try before checking the solutions.


hello_world/

# Print "hello world".
# Hint: There are many ways to print text on
# the command line, one way is with the 'echo'
# command.
# 
# Try it below and good luck!
# 
Solution:
echo "hello world"

current_working_directory/

# Print the current working directory.
#
Solution:
pwd

list_files/

# List all of the files in the current
# directory, one file per line.
#
Solution:
ls -1

last_lines/

# Print the last 5 lines of "access.log".
# 
Solution:
tail -5 access.log

find_string_in_a_file/

# There is a file named "access.log" in the
# current working directory. Print all lines
# in this file that contains the string "GET".
#
Solution:
grep GET access.log

search_for_files_containing_string/

# Print all files, one per line that contain
# the string "500".
# 
Solution:
grep -rl * -e 500

search_for_files_by_extension/

# Print the relative file paths, one path
# per line for all files that start with
# "access.log" in the current directory.
# 
Solution:
find . -name "access.log*"

search_for_string_in_files_recursive/

# Print all matching lines (without the filename
# or the file path) in all files under the current
# directory that start with "access.log" that
# contain the string "500".
# 
Solution:
find . -name "access.log*" | xargs grep -h 500

extract_ip_addresses/

# Extract all IP addreses from files that
# that start with "access.log" printing one
# IP address per line.
# 
Solution:
find . -name "access.log*" | xargs grep -Eo '^[^ ]+'

delete_files/

# Delete all of the files in this challenge
# directory including all subdirectories and
# their contents.
# 
Solution:
find . -delete

count_files/

# Count the number of files in the current
# working directory. Print the number of
# files as a single integer.
# 
Solution:
ls | wc -l

simple_sort/

# Print the contents of access.log
# sorted.
# 
Solution:
sort access.log

count_string_in_line/

# Print the number of lines
# in access.log that contain the string
# "GET".
# 
Solution:
grep GET access.log | wc -l

split_on_a_char/

# The file split-me.txt contains a list of
# numbers separated by a ';' character.
# Split the numbers on the ';' character,
# one number per line.
# 
Solution:
cat split-me.txt | sed s/\;/\\n/g

print_number_sequence/

# Print the numbers 1 to 100 separated
# by spaces.
# 
Solution:
echo {1..100}

remove_files_with_extension/

# There are files in this challenge with
# different file extensions.
# Remove all files with the .doc extension
# recursively in the current working directory.
#
Solution:
find . -name "*.doc" -delete

replace_text_in_files/

# This challenge has text files that contain
# the phrase "challenges are difficult". Delete
# this phrase recursively from all text files.
# 
Solution:
find . -name "*.txt" -exec sed -i 's/challenges are difficult//g' {} +

sum_all_numbers/

# The file sum-me.txt have a list of numbers,
# one per line. Print the sum of these numbers.
#
Solution:
cat sum-me.txt | xargs | sed -e 's/\ /+/g' | bc

just_the_files/

# Print all files in the current directory
# recursively without the leading directory path.
# 
Solution:
find . -type f -printf "%f\n"

remove_extensions_from_files/

# Remove the extension from all files in
# the current directory recursively.
# 
Solution: (note you cant use find .)
find `pwd` -type f -exec bash -c 'mv "$1" "${1%.*}"' - '{}' \;

replace_spaces_in_filenames/

# The files in this challenge contain spaces.
# List all of the files in the current
# directory but replace all spaces with a '.'
# character.
# 
Solution:
find . -type f -printf "%f\n" | xargs -0 -I {} echo {} | tr ' ' '.'

files_starting_with_a_number/

# There are a mix of files in this directory
# that start with letters and numbers. Print
# the filenames (just the filenames) of all
# files that start with a number recursively
# in the current directory.
# 
Solution:
find . -name '[0-9]*' -type f -printf "%f\n"

print_nth_line/

# Print the 25th line of the file faces.txt
# 
Solution:
sed '25q;d' faces.txt

remove_duplicate_lines/

# Print the file faces.txt, but only print the first instance of each
# duplicate line, even if the duplicates don't appear next to each other.
# 
Solution:
awk '!seen[$0]++' faces.txt

corrupted_text/

# You have a new challenge!
# The following excerpt from War and Peace is saved to
# the file 'war_and_peace.txt':
# 
# She is betraying us! Russia alone must save Europe.
# Our gracious sovereign recognizes his high vocation
# and will be true to it. That is the one thing I have
# faith in! Our good and wonderful sovereign has to
# perform the noblest role on earth, and he is so virtuous
# and noble that God will not forsake him. He will fulfill
# his vocation and crush the hydra of revolution, which
# has become more terrible than ever in the person of this
# murderer and villain!
# 
# The file however has been corrupted, there are random '!'
# marks inserted throughout.  Print the original text.
# 
Solution: (Found this on hackernews)
< war_and_peace.txt tr -s '!' | sed 's/!\([a-z]\)/\1/g' | sed 's/!\( [a-z]\)/\1/g' | sed 's/!\.!/./g' | sed 's/ !/ /g'


Also, you can checkout the creator's solutions here.

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