Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
How do I know if I am running a shell inside another shell?
Answer:
We can enter another a shell from a current shell, e.g. enter sh from a bash. To show the current "shell stack", you can use the pstree command.
# pstree -p | grep bash
|-sshd(791)---sshd(29118)---sshd(29171)---bash(29172)---sh(29428)-+-grep(29430)
List the size of sub directories in the current directory
Answer:
To check the disk usage of all sub directories in the current directory, you can try the following method:
# sudo du -h --max-depth=1
4.0K ./src
341M ./lib
68M ./bin
24K ./games
195M ./share
36M ./local
18M ./sbin
18M ./include
673M .How to kill and logout a logged in user
Answer:
Assume john is logged in and you want to terminate his session, you can use the skill command.
# sudo skill -KILL -u john
Simple environment variable usage in Linux
Answer:
In Linux, the most basic way to set an environment variable is use the "=" operator.
For example:
# foo=bar
# echo $foo
bar
Count the total number of logged in user
Answer:
To count the total number of logged in user(s), use the following commands:
# who | wc -l
3
It shows currently there are 3 users logged in.
