Linux Shell

Contents 1 Bash commands 2 Output 3 Loops 4 Combine find and some other command e.g chmod 5 sed 6 get filename without extension 7 Get Date as String 8 Tar 9 Pause

Bash commands

rm -rf dir   # do not show warning if not existing
mkdir -p dir # do not print warning if already existing AND make needed parents

Output

Send program output into file

sh script.sh > log.txt                     # std output, (errors to terminal)
sh script.sh 1> log.txt 2> log-errors.txt 
sh script.sh 1> log.txt 2>&1               # both into same file

Piping

sh script.sh | less 

Filtering of output

sh script.sh | grep tmenke 

Loops

Good overview of parameters for if [1]
If

if [ -d "backup.0" ]; then
  echo "gibts"
else 
  echo "gibts nicht"
fi

one-liner:

 if [ -d "backup.0" ] ; then sudo mv backup.0 backup.1 ; fi

While
Normal loop

i=1
while [ $i -le 4 ] do
(( i++ ))
done

Endless loop

while : do
...
done

For loop

for i in *.txt; 
  do 
  mv "$i" `echo $i | tr ' ' '_'`
  done

Combine find and some other command e.g chmod

find -type d -exec chmod g+xs {} \;

sed

If you want to replace the text 'asdf' by 'qwert' in all '*.txt' files in a directory at once, use the following command:

sed -i -e 's/asdf/qwert/g' *.txt

get filename without extension

for file in *
do
  if [ -f $file ] ; then
    name=${file%\.*} # name without extension
    echo ${name}
  fi ;
done

name=`basename /path/filename.ext .ext` # -> filename
for i in *.jpeg; do mv "$i" "`basename "$i" .jpeg`.jpg"; done

current_directory=$( pwd )

Get Date as String

DATE=`date +"%y-%m-%d_%H-%M"`
echo $DATE

Tar

get rid of message "removing leading /": use option P

Pause

read -p "Press any key to start backup..."