. . .Uses of some Build in Variables. . .
1. echo $LOGNAME and echo $USER -----> show's who is the logged in user
2. echo $HOSTNAME -----> show's the Hostname of the Linux Box
3. echo $PPID ----> show's the Process ID of Shell's Parent Directory ( If u kill this every logged in terminal will be closed)
4. echo $PWD ----> show's the Present Working Directory
5. echo $UID -----> show's the UserID of the currently Logged in user
6. echo $MAIL -----> Show's the Mail Path
7. echo $HISTFILE -----> Show's the file's which stores the history details
8. echo $HOME -----> show's the users HOME Directory
9. echo $PATH -----> A colon-separated list of directories in which the shell looks for commands.
10.echo $BASH The full pathname used to execute the current instance of Bash.
11.echo $HISTSIZE ----> This will show you the HISTORY size
12 $? ------> Expands to the exit status of the most recently executed foreground pipeline.
13. $$ -----> Shows to the process ID of the shell and if it used inside a script it shows the process ID of the script.
14. $! -----> Expands to the process ID of the most recently executed background command(&).
15. $0 -----> Expands to the name of the shell or shell script.
16. $_ -----> It will show you what is the Last Argument used [ like esc (.) or alt (.) ]
How to set a value for a variable in single command?
#echo ${raj:=rajkumar}
#echo $raj
How to assign o/p value of a command to a variable?
Syntax:
1. $(command)
2. `command`
#echo `date`
Sun May 1 13:12:31 IST 2011
#echo $(date)
Sun May 1 13:12:40 IST 2011
cat first.sh
#!bin/bash
a=`du -sh /home/rajm | awk {'print $1'}`
echo "I am User $USER and I am running this script"
echo "The UserID of $USER is $UID"
echo "The name of the Script is $0"
echo "The processID of the script $0 is: $$"
echo "The Script is running from $PWD directory"
echo "Size of User $LOGNAME Home directory($HOME) is :$a"
echo "Status of Previously executed command is: $?"
echo "The script $0 contains $LINENO Lines"
#sh first.sh
I am User rajm and I am running this script
The UserID of rajm is 516
The name of the Script is first.sh
The processID of the script first.sh is: 5096
The Script is running from /home/rajm/script/blog directory
Size of User rajm Home directory(/home/rajm) is :696M
Status of Previously executed command is: 0
The script first.sh contains 10 Lines
1. echo $LOGNAME and echo $USER -----> show's who is the logged in user
2. echo $HOSTNAME -----> show's the Hostname of the Linux Box
3. echo $PPID ----> show's the Process ID of Shell's Parent Directory ( If u kill this every logged in terminal will be closed)
4. echo $PWD ----> show's the Present Working Directory
5. echo $UID -----> show's the UserID of the currently Logged in user
6. echo $MAIL -----> Show's the Mail Path
7. echo $HISTFILE -----> Show's the file's which stores the history details
8. echo $HOME -----> show's the users HOME Directory
9. echo $PATH -----> A colon-separated list of directories in which the shell looks for commands.
10.echo $BASH The full pathname used to execute the current instance of Bash.
11.echo $HISTSIZE ----> This will show you the HISTORY size
12 $? ------> Expands to the exit status of the most recently executed foreground pipeline.
13. $$ -----> Shows to the process ID of the shell and if it used inside a script it shows the process ID of the script.
14. $! -----> Expands to the process ID of the most recently executed background command(&).
15. $0 -----> Expands to the name of the shell or shell script.
16. $_ -----> It will show you what is the Last Argument used [ like esc (.) or alt (.) ]
How to set a value for a variable in single command?
#echo ${raj:=rajkumar}
#echo $raj
How to assign o/p value of a command to a variable?
Syntax:
1. $(command)
2. `command`
#echo `date`
Sun May 1 13:12:31 IST 2011
#echo $(date)
Sun May 1 13:12:40 IST 2011
cat first.sh
#!bin/bash
a=`du -sh /home/rajm | awk {'print $1'}`
echo "I am User $USER and I am running this script"
echo "The UserID of $USER is $UID"
echo "The name of the Script is $0"
echo "The processID of the script $0 is: $$"
echo "The Script is running from $PWD directory"
echo "Size of User $LOGNAME Home directory($HOME) is :$a"
echo "Status of Previously executed command is: $?"
echo "The script $0 contains $LINENO Lines"
#sh first.sh
I am User rajm and I am running this script
The UserID of rajm is 516
The name of the Script is first.sh
The processID of the script first.sh is: 5096
The Script is running from /home/rajm/script/blog directory
Size of User rajm Home directory(/home/rajm) is :696M
Status of Previously executed command is: 0
The script first.sh contains 10 Lines
