Useful GNU Bash Scripts

Shell Scripts.sh

# Common Contents of two text files -------------
diff -y -w --strip-trailing-cr -i --minimal --color=always file1 file2 | grep -n -v'' "[|<>]"                                                       

diff --ignore-blank-lines --ignore-space-change --ignore-trailing-space --ignore-case --minimal --strip-trailing-cr --unchanged-group-format='@@ %dn, %df
%<' --old-group-format='' --new-group-format='' --changed-group-format=''  file1 file2
# -------------------------------------------

# CSV like parsing
sed 's/,,/, ,/g;s/,,/, ,/g' data.csv | column -s, -t

# list all files with type without preceding ./
find -name '*.type' | sed 's/\.\///'

# find and delete files with size less than k
find . -type f -size -30k -maxdepth 1 -exec rm -r {} \;

# count #lines
wc -l

# grep recursively over all files in a directory
grep -nrwi 'pattern' `ls`
grep -nrwi 'pattern' `find . -name '*'`

# string tokenize
IFS=';' tokens=( $string )
echo ${tokens[*]}

# iterate over lines
IFS=$'\n'       # make newlines the only separator
for line in $(cat filename)    
do
    echo "$line"
done

# has process substitution
while read i; do echo "$i"; done < filename

# has process substitution
cat filename | while read -r j
do
    echo $j
done

# iterate without process substitution
while read -r line
do
  printf '%s\n' "$line"
done < <(ioscan -m dsf)


# rename all files in a directory
rename 's/text/with\ text/g' *.jpg

find . -name '*jpg' -exec bash -c ' mv $0 ${0/text/with}' {} \;

find . -type f -name 'Lucky-*' | while read FILE ; do
    newfile="$(echo ${FILE} |sed -e 's/text/with/')" ;
    mv "${FILE}" "${newfile}" ;
done 


# number of files in a directory
ls -1 `ls test/` | wc -l


# check if directory/file exists
if [ ! -d "path/to/file_or_dir" ] 
then
   echo "path/to/file_or_dir"
fi


# download if not exists
wget -nc https://url/


# copy folder contents to another folder
cp -a /source/. /dest/ # just contents
cp -R "$source" dest # also source folder


# unzip to a directory
unzip "path/to/zip" -d dest/


# ------- create symlink ------------
ln -s /mnt/my_drive/movies ~/my_movies # softlink
unlink symlink_to_remove
rm symlink_to_remove


# ------- user management -----------
# create new user
sudo useradd -m subangkar -p PASSWORD
sudo useradd subangkar

# set passwd of user
sudo passwd subangkar

# create new group
sudo groupadd newgroup

# add user to group
usermod -a -G grp1,grp2 username