How to use positional parameters
From Linux Shell Scripting Tutorial - A Beginner's handbook
All command line parameters ( positional parameters ) are available via special shell variable $1, $2, $3,...,$9.
How Do I Access Command-Line Arguments
Create a simple shell script called cmdargs.sh:
#!/bin/bash echo "The script name : $0" echo "The value of the first argument to the script : $1" echo "The value of the second argument to the script : $2" echo "The value of the third argument to the script : $3" echo "The number of arguments passed to the script : $#" echo "The value of all command-line arguments (\$* version) : $*" echo "The value of all command-line arguments (\$@ version) : $@"
Save and close the file. Rut it as follows:
chmod +x cmdargs.sh ./cmdargs.sh bmw ford toyota
Sample outputs:
The script name : ./cmdargs.sh The value of the first argument to the script : bmw The value of the second argument to the script : ford The value of the third argument to the script : toyota The number of arguments passed to the script : 3 The value of all command-line arguments ($* version) : bmw ford toyota The value of all command-line arguments ($@ version) : bmw ford toyota
Try the following examples:
ls /tmp ./math 10 + 3 ~/scripts/addzone cyberciti.com ~/scripts/adddomain cyberciti.biz '74.86.48.99' '2607:f0d0:1002:11::4' /etc/init.d/named reload /usr/local/etc/rc.d/jail restart cyberciti.biz
| Shell script name ($0) | Total number of arguments ($#) | Actual Command line argument ($1,..,$9) | ||
|---|---|---|---|---|
| ls | 1 | /tmp | ||
| ./math | 3 | 10, +, and 3 | ||
| ~/scripts/addzone | 1 | cyberciti.com | ||
| ~/scripts/adddomain | 3 | cyberciti.biz, 74.86.48.99, and 2607:f0d0:1002:11::4 | ||
| /etc/init.d/named reload | 1 | reload | ||
| /usr/local/etc/rc.d/jail | 2 | restart, and cyberciti.biz | ||
A Note About $@ and $*
- $@ expanded as "$1" "$2" "$3" ... "$n"
- $* expanded as "$1y$2y$3y...$n", where y is the value of $IFS variable i.e. "$*" is one long string and $IFS act as an separator or token delimiters.
Example: The Difference Between $@ and $*
Create a shell script called pizza.sh:
#!/bin/bash IFS=", " echo "* Displaying all pizza names using \$@" echo "$@" echo echo "* Displaying all pizza names using \$*" echo "$*"
Save and close the file. Run it as follows:
chmod +x pizza.sh ./pizza.sh Margherita Tomato Panner Gourmet
Sample outputs:
* Displaying all pizza names using $@ Margherita Tomato Panner Gourmet *Displaying all pizza names using $* Margherita,Tomato,Panner,Gourmet
