shell - not found error when insert #!/bin/sh -

i started learning linux shell scripting, when writing script got error,

./my_script: 4: read: illegal option -n ./my_script: 5: ./my_script: [[: not found 

i found out because #!/bin/sh line, can still run script without line won't execute codes such /n

#!/bin/sh # shell installer gurb customizer. naveen gamage.  os=$(lsb_release -si) arch=$(uname -m | sed 's/x86_//;s/i[3-6]86/32/') ver=$(lsb_release -sr)  grabninstall() {     sudo add-apt-repository ppa:danielrichter2007/grub-customizer     sudo apt-get update     sudo apt-get install grub-customizer     }  echo "installer grub customizer\n" echo "gurb customizer" echo "a tool editing , configuring boot menu (grub2/burg).\n"  read -p "do want install grub customizer $os ${ver} [$arch] ? (y/n) " -n 1  if [[ $reply =~ ^[yy]$ ]]     echo "the installer downloading , installing grub customizer!";     echo "this action may require password.\n";     grabninstall else     echo "user quit"     echo "installation unsuccessful." fi 

i'm doing on ubuntu 12.10.

and which sh gives output

/bin/sh 

any idea did wrong?

the problem using /bin/sh run script , on system /bin/sh -> dash. means dash executing script. dash shell not support [[, bash does. should change first line in script (called shebang) #!/bin/sh #!/bin/bash.

alternatively, don't use [[ in script. use features support dash.

also see this ubuntu page on constructs not supported in dash.