A script to add user in Linux

# Path to files
pfile=/etc/passwd
gfile=/etc/group
sfile=/etc/shells

# Paths to binaries
useradd=/usr/sbin/useradd
chfn=/usr/bin/chfn
passwd=/usr/bin/passwd
chmod=/bin/chmod

# Defaults
defhome=/home
defshell=/bin/bash
defchmod=711 # home dir permissions - may be preferable to use 701, however.
defgroup=users
AGID="audio cdrom floppy plugdev video" # additional groups for desktop users

# Determine what the minimum UID is (for UID recycling)
# (we ignore it if it's not at the beginning of the line (i.e. commented out with #))
export recycleUIDMIN="$(grep ^UID_MIN /etc/login.defs | awk '{print $2}' 2>/dev/null)"
# If we couldn't find it, set it to the default of 1000
if [ -z "$recycleUIDMIN" ]; then
 export recycleUIDMIN=1000 
fi


# This setting enables the 'recycling' of older unused UIDs.
# When you userdel a user, it removes it from passwd and shadow but it will
# never get used again unless you specify it expliticly -- useradd (appears to) just
# look at the last line in passwd and increment the uid.  I like the idea of
# recycling uids but you may have very good reasons not to (old forgotten
# confidential files still on the system could then be owned by this new user).
# We'll set this to no because this is what the original adduser shell script
# did and it's what users expect.
recycleuids=no

# Function to read keyboard input.
# bash1 is broken (even ash will take read -ep!), so we work around
# it (even though bash1 is no longer supported on Slackware).
function get_input() {
local output
if [ "`echo $BASH_VERSION | cut -b1`" = "1" ]; then
  echo -n "${1} " >&2 # fudge for use with bash v1
  read output
else # this should work with any other /bin/sh
  read -ep "${1} " output
fi
echo $output
}

# Function to display the account info
function display () {
local goose
goose="$(echo $2 | cut -d ' ' -f 2-)"  # lop off the prefixed argument useradd needs
echo -n "$1 "
# If it's null then display the 'other' information
if [ -z "$goose" -a ! -z "$3" ]; then
  echo "$3"
else
  echo "$goose"
fi
}

# Function to check whether groups exist in the /etc/group file
function check_group () {
local got_error group
if [ ! -z "$@" ]; then
for group in $@ ; do
  local uid_not_named="" uid_not_num=""
  grep -v "$^" $gfile | awk -F: '{print $1}' | grep "^${group}$" >/dev/null 2>&1 || uid_not_named=yes
  grep -v "$^" $gfile | awk -F: '{print $3}' | grep "^${group}$" >/dev/null 2>&1 || uid_not_num=yes
  if [ ! -z "$uid_not_named" -a ! -z "$uid_not_num" ]; then
    echo "- Group '$group' does not exist"
    got_error=yes
  fi
done
fi
# Return exit code of 1 if at least one of the groups didn't exist
if [ ! -z "$got_error" ]; then
  return 1
fi
} 

#: Read the login name for the new user :#
#
# Remember that most Mail Transfer Agents are case independant, so having
# 'uSer' and 'user' may cause confusion/things to break.  Because of this,
# useradd from shadow-4.0.3 no longer accepts usernames containing uppercase,
# and we must reject them, too.

# Set the login variable to the command line param
echo
LOGIN="$1"
needinput=yes
while [ ! -z $needinput ]; do
if [ -z "$LOGIN" ]; then
  while [ -z "$LOGIN" ]; do LOGIN="$(get_input "Login name for new user []:")" ; done
fi
grep "^${LOGIN}:" $pfile >/dev/null 2>&1  # ensure it's not already used
if [ $? -eq 0 ]; then
  echo "- User '$LOGIN' already exists; please choose another"
  unset LOGIN
elif [ ! -z "$( echo $LOGIN | grep "^[0-9]" )" ]; then
  echo "- User names cannot begin with a number; please choose another"
  unset LOGIN
elif [ ! "$LOGIN" = "`echo $LOGIN | tr A-Z a-z`" ]; then # useradd does not allow uppercase
  echo "- User '$LOGIN' contains illegal characters (uppercase); please choose another"
  unset LOGIN
elif [ ! -z "$( echo $LOGIN | grep '\.' )" ]; then
  echo "- User '$LOGIN' contains illegal characters (period/dot); please choose another"
  unset LOGIN
else
  unset needinput
fi
done

# Display the user name passed from the shell if it hasn't changed
if [ "$1" = "$LOGIN" ]; then
echo "Login name for new user: $LOGIN"
fi

#: Get the UID for the user & ensure it's not already in use :#
#
# Whilst we _can_ allow users with identical UIDs, it's not a 'good thing' because
# when you change password for the uid, it finds the first match in /etc/passwd
# which isn't necessarily the correct user
#
echo
needinput=yes
while [ ! -z "$needinput" ]; do
_UID="$(get_input "User ID ('UID') [ defaults to next available ]:")"
grep -v "^$" $pfile | awk -F: '{print $3}' | grep "^${_UID}$" >/dev/null 2>&1
if [ $? -eq 0 ]; then
  echo "- That UID is already in use; please choose another"
elif [ ! -z "$(echo $_UID | egrep '[A-Za-z]')" ]; then
  echo "- UIDs are numerics only"       
else
  unset needinput
fi
done
# If we were given a UID, then syntax up the variable to pass to useradd
if [ ! -z "$_UID" ]; then
U_ID="-u ${_UID}"
else
# Will we be recycling UIDs?
if [ "$recycleuids" = "yes" ]; then
  U_ID="-u $(awk -F: '{uid[$3]=1} END { for (i=ENVIRON["recycleUIDMIN"];i in uid;i++);print i}' $pfile)"
fi 
fi

#: Get the initial group for the user & ensure it exists :#
#
# We check /etc/group for both the text version and the group ID number
echo
needinput=yes
while [ ! -z "$needinput" ]; do
GID="$(get_input "Initial group [ ${defgroup} ]:")"
check_group "$GID"
if [ $? -gt 0 ]; then
  echo "- Please choose another"
else
  unset needinput
fi
done
# Syntax the variable ready for useradd
if [ -z "$GID" ]; then
GID="-g ${defgroup}"
else
GID="-g ${GID}"
fi

#: Get additional groups for the user :#
#
echo "Additional UNIX groups:"
echo
echo "Users can belong to additional UNIX groups on the system."
echo "For local users using graphical desktop login managers such"
echo "as XDM/KDM, users may need to be members of additional groups"
echo "to access the full functionality of removable media devices."
echo
echo "* Security implications *"
echo "Please be aware that by adding users to additional groups may"
echo "potentially give access to the removable media of other users."
echo
echo "If you are creating a new user for remote shell access only,"
echo "users do not need to belong to any additional groups as standard,"
echo "so you may press ENTER at the next prompt."
echo
needinput=yes
while [ ! -z "$needinput" ]; do
history -c
history -s "$AGID"
echo "Press ENTER to continue without adding any additional groups"
echo "Or press the UP arrow to add/select/edit additional groups"
AGID="$(get_input ": " | tr -d '[:punct:]' | tr -s ' ' | sed 's?^ $??g' )"
if [ ! -z "$AGID" ]; then
  check_group "$AGID" # check all groups at once (treated as N # of params)
  if [ $? -gt 0 ]; then
    echo "- Please re-enter the group(s)"
    echo
  else
    unset needinput # we found all groups specified
    AGID="-G $(echo $AGID | tr ' ' ,)" # useradd takes comma delimited groups
  fi
else
  unset needinput # we don't *have* to have additional groups
fi
done

#: Get the new user's home dir :#
#     
echo
needinput=yes
while [ ! -z "$needinput" ]; do
HME="$(get_input "Home directory [ ${defhome}/${LOGIN} ]")"
if [ -z "$HME" ]; then
  HME="${defhome}/${LOGIN}"
fi
# Warn the user if the home dir already exists
if [ -d "$HME" ]; then
  echo "- Warning: '$HME' already exists !"
  getyn="$(get_input "  Do you wish to change the home directory path ? (Y/n) ")"
  if [ "$(echo $getyn | grep -i "n")" ]; then
    unset needinput
    # You're most likely going to only do this if you have the dir *mounted* for this user's $HOME
    getyn="$(get_input "  Do you want to chown $LOGIN.$( echo $GID | awk '{print $2}') $HME ? (y/N) ")"
    if [ "$(echo $getyn | grep -i "y")" ]; then
       CHOWNHOMEDIR=$HME # set this to the home directory
    fi
  fi
else
  unset needinput
fi
done         
HME="-d ${HME}"

#: Get the new user's shell :#
echo
needinput=yes
while [ ! -z "$needinput" ]; do
unset got_error
SHL="$(get_input "Shell [ ${defshell} ]")"
if [ -z "$SHL" ]; then
  SHL="${defshell}"
fi
# Warn the user if the shell doesn't exist in /etc/shells or as a file
if [ -z "$(grep "^${SHL}$" $sfile)" ]; then
  echo "- Warning: ${SHL} is not in ${sfile} (potential problem using FTP)"
  got_error=yes
fi
if [ ! -f "$SHL" ]; then
  echo "- Warning: ${SHL} does not exist as a file"
  got_error=yes
fi
if [ ! -z "$got_error" ]; then
  getyn="$(get_input "  Do you wish to change the shell ? (Y/n) ")"
  if [ "$(echo $getyn | grep -i "n")" ]; then
    unset needinput
  fi
else
  unset needinput
fi
done         
SHL="-s ${SHL}"

#: Get the expiry date :#
echo
needinput=yes
while [ ! -z "$needinput" ]; do
EXP="$(get_input "Expiry date (YYYY-MM-DD) []:")"
if [ ! -z "$EXP" ]; then
  # Check to see whether the expiry date is in the valid format
  if [ -z "$(echo "$EXP" | grep "^[[:digit:]]\{4\}[-]\?[[:digit:]]\{2\}[-]\?[[:digit:]]\{2\}$")" ]; then
    echo "- That is not a valid expiration date"
  else
    unset needinput
    EXP="-e ${EXP}"
  fi
else
  unset needinput
fi
done

# Display the info about the new impending account
echo
echo "New account will be created as follows:"
echo
echo "---------------------------------------"
display "Login name.......: " "$LOGIN"
display "UID..............: " "$_UID" "[ Next available ]"
display "Initial group....: " "$GID"
display "Additional groups: " "$AGID" "[ None ]"
display "Home directory...: " "$HME"
display "Shell............: " "$SHL"
display "Expiry date......: " "$EXP" "[ Never ]"
echo

echo "This is it... if you want to bail out, hit Control-C.  Otherwise, press"
echo "ENTER to go ahead and make the account."
read junk

echo
echo "Creating new account..."
echo
echo

# Add the account to the system
CMD="$useradd "$HME" -m "$EXP" "$U_ID" "$GID" "$AGID" "$SHL" "$LOGIN""
$CMD

if [ $? -gt 0 ]; then
echo "- Error running useradd command -- account not created!"
echo "(cmd: $CMD)"
exit 1
fi

# chown the home dir ?  We can only do this once the useradd has
# completed otherwise the user name doesn't exist.
if [ ! -z "${CHOWNHOMEDIR}" ]; then
chown "$LOGIN"."$( echo $GID | awk '{print $2}')" "${CHOWNHOMEDIR}"
fi

# Set the finger information
$chfn "$LOGIN"
if [ $? -gt 0 ]; then
echo "- Warning: an error occurred while setting finger information"
fi

# Set a password
$passwd "$LOGIN"
if [ $? -gt 0 ]; then
echo "* WARNING: An error occured while setting the password for"
echo "           this account.  Please manually investigate this *"
exit 1
fi

# If it was created (it should have been!), set the permissions for that user's dir
HME="$(echo "$HME" | awk '{print $2}')"  # We have to remove the -g prefix
if [ -d "$HME" ]; then
$chmod $defchmod "$HME"
fi

echo
echo
echo "Account setup complete."
exit 0