Shell Programming and Scripting

# ---------- ---------- ----------
# root not allowed to run this
# ---------- ---------- ----------
[[ $( whoami ) = root ]] && exit 2

# ---------- ---------- ----------
# Don't run this in /tmp
# ---------- ---------- ----------
[[ $( pwd ) = /tmp* ]] && exit 3

# ---------- ---------- ----------
# Don't run as sudo
# ---------- ---------- ----------


# ---------- ---------- ----------
# How much space is available here?
#
# Filesystem    Type   1K-blocks      Used Available Use% Mounted on
# /dev/sda3     ext3    68588072  32259392  32788356  50% /home
# ---------- ---------- ----------
integer _avail=$( df -k . | grep -v "^Filesystem" | awk '{ print $4 }' )
integer _threshold=26214400  # 25GB
(( _avail < _threshold )) && {

    print -u2 "***> There is not enough space (25gb) on this mount point!"
    print -u2 "     Only found ${_avail} kb."
    exit 4

}

ant:/home/vbe $ whoami
root
ant:/home/vbe $ who am i
vbe        pts/2        May 19 10:25

>whoami
eric

>sudo echo $( whoami )
eric

$ echo $(id -u)
1000
$ sudo echo $(id -u)
0

[ $(id -u) -eq 0 ] && exit 2
# or
$(($(id -u))) || exit 2