Writing Unix Shell script

Objectives
• Start a script with #!
• Put comments in a script
• Put commands in a script
• Change permissions on the script
• Execute a script
• Debug a script
Creating Shell Scripts
• Create a file using any text editor
• Put UNIX commands, user programs, or the names of
other scripts as commands in the file
• Save the file, and exit from the editor
$ vi firstscript.sh

$ cat firstscript.sh
#!/bin/sh
clear
echo "SCRIPT BEGINS"
echo "Hello $LOGNAME!"
echo
echo "Todays date and time: \c"
date
echo
mynum=21
myday="Monday"
echo "The value of mynum is $mynum"
echo "The value of myday is $myday"
echo
echo "SCRIPT FINISHED!!"
echo

Executing a Shell Script
• Give the script execute permission
• Execute the script as a command
• Create a subshell in which to execute the script

Executing firstscript.sh
$ cat firstscript.sh
#!/bin/sh
clear
echo "SCRIPT BEGINS"
echo "Hello $USER!"
echo
echo "Todays date and time: \c"
date
echo
mynum=21
myday="Monday"
echo "The value of mynum is $mynum"
echo "The value of myday is $myday"
echo
echo "SCRIPT FINISHED!!"
echo