Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
Repeat previous command in Bash
Answer:
It is easy to type !! when you want to repeat the previous executed command in Bash
# ls -l /var/log/messages
-rw-r----- 1 syslog adm 330 Mar 29 17:17 /var/log/messages
# !!
ls -l /var/log/messages
-rw-r----- 1 syslog adm 330 Mar 29 17:17 /var/log/messages
How to unset an environment variable in bash
Answer:
To unset an environment variable in bash, you can use the unset command.
Example:
# export foo=bar
# echo $foo
bar
# unset foo
# echo $foo
How to check the bash shell version
Answer:
To check the current bash shell version
# bash -version
GNU bash, version 3.2.48(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2007 Free Software Foundation, Inc.
How to execute a command repeatedly using bash
Answer:
The following simple bash script will run the echo command, sleep 10 seconds repeatedly.
#!/bin/bash
while [1];
do
echo "Hello!";
sleep 10;
done
How to get the PID in current bash shell script
Answer:
Use the special variable $$, you can get the PID (Process ID) of the current bash shell script
#/bin/bash
echo $$;
The above script will print the PID to the standard out.
