HACKTUX notes from the trenches

Below are examples of the Bash for loop in action. If you need more help, see the official Bash documentation for an introduction to Bash programming.

Examples

Echo all jpg files in the current folder:

for JPG in *.jpg; do
  echo $JPG
done

Count a list of numbers:

for NUM in $(seq 1 10); do
  echo $NUM
done

One liners work as well:

for n in $(seq 3); do echo $n; done

Iterate through the process ID's for httpd and kill them:

for PID in $(ps -C httpd | awk '/httpd/ { print $1 }'); do
  kill -TERM $PID
done

List arguments to a function named showarg:

showarg() {
  for ARG in $@; do
    echo $ARG
  done
}

Loop through folders and back them up using tar:


DATE=$(date +'%Y-%m-%d')
for DIR in /etc /var /root; do
  tar -czvf /backups/$DIR_$DATE.tgz $DIR
done