Create/Delete Users from Text File Using Bash Script

Create/delete users from text file using Bash script

After you read in the name of the file you have to iterate through that file and create or delete user for each line of the file.

Example :

for user in `cat user_list`
do
    sudo useradd "$user" -m -p "$user"
done

How to delete users listed in a file ( Ubuntu Bash):

You can use a while loop and read the file userstobedel.txt line by line:

while IFS= read -r usertobedel
do
    deluser "$usertobedel"
done < userstobedel.txt

IFS= and -r are explained here.

BASH Script to Remove old files, and create a text file containing the count and size of total files deleted.

I would use the below script, say deleter.sh for the purpose :

#!/bin/bash
myfunc()
{
  local totalsize=0
  echo " Removing files listed below "
  echo "${@}"
  sizes=( $(stat --format=%s "${@}") ) #storing sizes in an array.
  for i in "${sizes[@]}"
  do
  (( totalsize += i )) #calculating total size.
  done
  echo "Total space to be freed : $totalsize bytes"
  rm "${@}"
  if [ $? -eq 0 ]  #$? is the return value
    then
  echo "All files deleted"
  else
    echo "Some files couldn't be deleted"
  fi
}
export -f myfunc
find "$1" -type f -not -name "*deleter.sh" -mtime +60\
-exec bash -c 'myfunc "$@"' _ {} +
# -not -name "*deleter.sh" to prevent self deletion
# Note -mtime +60 for files older than 60 days.

Do

chmod +x ./deleter.sh

And run it as

./deleter '/path/to/your/directory'

References

1. Find [ manpage ] for more info.
2. stat --format=%s gives size in bytes which we store in an array. See [ stat ] manpage.

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Delete a newly created file using shell script after 5 minutes

Using at command:

#!/usr/bin/env bash
script_path="$(realpath -s -- "$0")"
# start script
...
# end script
echo "rm -- \"$script_path\"" | at "now + 5 minutes"

Using background process with sleep:

#!/usr/bin/env bash
script_path="$(realpath -s -- "$0")"
# start script
...
# end script
( sleep 300 && rm -- "$script_path" ) &

Using parent selfdestruct process:

Write a little script selfdestruct that looks like:

#!/usr/bin/env bash
dt="$1"; shift
"$@"
( sleep "$dt" && rm -- "$1" ) &

and run your script with

$ selfdestruct 300 /path/to/script arg1 arg2 arg3

Create users based on a text file using Bash script?

#!/bin/bash
while IFS=: read username fullname usergroups
do
    useradd -G $usergroups -c "$fullname" $username
done < users.txt

fullname is the only string that should contains whitespace (hence the quotes), A list of usergroups should be separated from the next by a comma, with no intervening whitespace (so no quotes on that argument) and your username should not contain whitespace either.

Upate:

To get the list of usergroups to create first you can do this...

#!/bin/bash
while IFS=: read username fullname usergroups
do
    echo $usergroups >> allgrouplist.txt
done < users.txt

while IFS=, read group
do
   echo $group >> groups.txt
done < allgrouplist.txt

sort -u groups.txt | while read group
do
   groupadd $group
done

This is a bit long winded, and could be compacted to avoid the use of the additional files allgrouplist.txt and groups.txt but I wanted to make this easy to read. For reference here's a more compact version.

sort -u < $(
       echo $(while IFS=: read a b groups; do echo $groups; done < users.txt )
      | while IFS=, read group; do echo $group; done ) 
| while read group
do
       groupadd $group
done

_{(I screwed the compact version up a bit at first, it should be fine now, but please note I haven't tested this!)}

Delete text in file using bash script in CentOS

sed -i '/^zone "friedrice.com"/,/^}/d' you.txt

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