You'll need a shell script/function that iterates over the assigned range from UIDLOW to UIDHIGH and stops when it finds a free UID.
How about something like this:
#!/bin/sh
iterateUID () {
UIDLOW="$1"
UIDHIGH="$2"
ASSIGN_UID=none
CURR_UID="$UIDLOW"
while [ "$CURR_UID" -lt "$UIDHIGH" ]; do
grep -q "^[^:]*:[^:]*:$CURR_UID:" /etc/passwd
if [ $? = 0 ]; then
# UID is in use
CURR_UID=$( expr "$CURR_UID" + 1 )
continue
else
# found an UID
ASSIGN_UID="$CURR_UID"
break
fi
done
if [ "$ASSIGN_UID" = "none" ]; then
# could not find an UID
echo "ERROR: could not find a free UID. Range full?" >&2
echo "none"
return 1
fi
echo "$ASSIGN_UID"
return 0
}
If the function manages to find a suitable UID, it outputs it to stdout. If no free UID was found, it outputs an error message to stderr, sends the string "none" to stdout and returns with an error code.
After defining this function near the beginning of your script, you can use it like this:
# to find an UID between 100 and 200
USER_UID=$( iterateUID 100 200 )
if [ $? -gt 0 ]; then
# things to do if no UID found
fi
There are probably other, more resource-saving ways to do this.
For GIDs, change the variable names as appropriate and the "grep" line to:
grep -q "^[^:]*:[^:]*:$CURR_GID:" /etc/group
MK
MK
