UNIX for Dummies Questions & Answers

env -i $0
unalias $( alias | sed -e 's/^alias//' | cut -d= -f1 )
unset $( env | cut -d= -f1 )

# Run the current shell (which has it's name in $0) again, in an clean
# environment. User-specific configuration will still be read. See man env 
env -i ${0#-}

# alias lists all currently set aliases. sed will remove the string "alias"
# from the beginning of the line, and cut will only return the stuff up to the
# equal sign. The result of that is passed to unalias to unset those 
unalias $( alias | sed -e 's/^alias//' | cut -d= -f1 )

# env will return the complete environment. Cut will return only the variable
# names, which are then passend to unset to be removed from the environment 
unset $( env | cut -d= -f1 )

pludi@desktop:/tmp> env | wc -l; alias | wc -l
89
19
pludi@desktop:/tmp> env -i ${0#-}
pludi@desktop:/tmp> unalias $( alias | sed -e 's/^alias//' | cut -d= -f1 )
pludi@desktop:/tmp> unset $( env | cut -d= -f1 )
pludi@desktop:/tmp> env | wc -l; alias | wc -l
bash: wc: No such file or directory
bash: env: No such file or directory
bash: wc: No such file or directory
pludi@desktop:/tmp> /usr/bin/env | /usr/bin/wc -l; alias | /usr/bin/wc -l
1
0