Usefull linux commands for everyone

linux-cheatsheet.sh

# for informations
sudo lshw                       # hardware informations to standard output
sudo lshw -html > hw.html       # hardware informations to html file
sudo lshw -xml > hw.xml         # hardware informations to xml file

lsb_release -a                  # information about your linux distribution

cat /proc/cpuinfo               # informations about your CPU
lscpu                           # informations about your CPU

# for fun
apt-get moo                     # just big moooo

# pdf
pdftk largepdfile.pdf burst               # splitting large pdf file into smaller ones
pdftk *.pdf cat output big.pdf            # merging many pdf files into one

# converting
convert input.jpg output.png                      # converts image to image (jpg to png)
convert input.png -resize 85% output.png          # makes output.png smaller (85% of input.png) then input.png 
convert img.png wasimg.pdf                        # converting image to pdf file
convert wasimg.pdf img.png                        # converting pdf file to image
convert -density 300 -quality 100 in.pdf out.png  # be sure that output has good quality use atributes (density, quality)

# download videos from youtube
youtube-dl <video_url>          # download video at specific video url
youtube-dl -F <video_url>       # list all video qualities for downloading
youtube-dl -f 22 <video_url>    # donwload video at url with quality 22 what means best

# converting html to pdf
wkhtmltopdf https://www.google.com google.pdf # converting web page to pdf
wkhtmltopdf file://google.html google.pdf     #  converting local html to pdf

# Strings / files
egrep -l "search_for" *file_pattern_to_search_in # search in files in one directory that match pattern *file_pattern_to_search_in for string search_for
sed -i".bak" '$a\something' <file_name>          # add string something to file filen_name at the end
find . -name \* -print                           # print recursively all files in directory . 
cat file1 file2 > big-one                        # file1 + file2 == big-one
grep -c "<search_string>" file_pattern           # count lines that match search_string in files that match file_pattern
grep -e "<search_string>" pattern1 pattern2      # search search_string in files that match pattern1 or pattern2
grep -n "<search_string>" pattern                # search search_string in files that match pattern and results output have line numbers

du -sh -c <dir>               # count total size of directory (human readable)
find <dir> -type f | wc -l    # count all files in directory

netstat -vulntp               # list all open ports
nc -vz <host> <port>          # is host:port open ?