Bash - While

This article is dedicated to the while syntax in Bash.

Bash - Sequence

count=0  
while [ $count -le 10 ]  
do  
    echo "$count"
    count=$(( $count + 1 ))
done  

done=0
while : ; do
  ...
  if [ "$done" -ne 0 ]; then
      break
  fi
done

where:

• : is the no-op command; its exit status is always 0

The command:

• lists the file with the ls executable (ls -l)
• pipe the output to the condition of thewhile statement
• where the condition is the read built-in command that splits the input into field (word) by line and stores the line content in the lineVariable variable

ls -l | while read -r lineVariable; do
    echo Line: $lineVariable
done

Line: -rw-r--r-- 1 root root 1849173 May 13 2015 unixODBC-2.3.2.tar.gz
Line: -rwxr-xr-- 1 oracle oinstall 64 May 16 2017 whileDemo.sh

Linux process monitoring (replace pid with your pid)

pid=22018
count=0
while kill -0 $pid 2> /dev/null; do
    count=$(( $count + 1 ))
    echo "${count} - Process is running"
    sleep 10
done
echo "${count} - Process has exited"

ls -l | while read -r permission child owner group size monthDate dayDate rest; do
    echo Line: 
    echo '    - Permission: '$permission
    echo '    - Child: '$child
    echo '    - Owner: '$owner
    echo '    - Group: '$group
    echo '    - Size: '$size
    echo '    - Month of Date: '$monthDate
    echo '    - Day of Date: '$dayDate
    echo '    - Rest: '$rest
done

Line:
    - Permission: -rw-r--r--
    - Child: 1
    - Owner: root
    - Group: root
    - Size: 1849173
    - Month of Date: May
    - Day of Date: 13
    - Rest: 2015 unixODBC-2.3.2.tar.gz
Line:
    - Permission: -rwxr-xr--
    - Child: 1
    - Owner: oracle
    - Group: oinstall
    - Size: 457
    - Month of Date: May
    - Day of Date: 16
    - Rest: 2017 whileDemo.sh

How to converse a Csv to XML ¹⁾

file_in="simple.csv"
file_out="simple.xml"
echo '<?xml version="1.0"?>' > $file_out
echo '<Customers>' >> $file_out
while IFS=$',' read -r -a arry
do
  echo '  <Customer>' >> $file_out
  echo '    <Name>'${arry[0]}'</Name>' >> $file_out
  echo '    <Age>'${arry[1]}'</Age>' >> $file_out
  echo '    <Country>'${arry[2]}'</Country>' >> $file_out
  echo '  </Customer>' >> $file_out
done < $file_in
echo '</Customers>' >> $file_out

while list; do list; done

The while command continuously executes the do list as long as the last command in list returns an exit status of zero.

The exit status of the while and until commands is the exit status of the last do list command executed, or zero if none was executed.