mjhjmtu

i wrote little shell code but i need to change variable while calling code how to do it

Example

./shell.sh --varaible="New Value"

should output

New Value,Some Value

shell.sh

variable="Old Value"
variable2="Some Value"

echo "$variable,$variable2"

It is not possible to change the value of a variable in a script from the command line if the script is explicitly setting the value of that variable.

You may, however, set the value of the variable in such a way that it takes the command line arguments into account.

The arguments given on the command line will be available to the shell script in the positional parameters $1, $2, $3 etc.

To set a variable to the first positional parameter, you would use

variable="$1"

So, your script might look like

#!/bin/sh

variable="$1"
variable2="Some Value"

echo "$variable,$variable2" # or printf '%s,%sn' "$variable" "$variable2"

... and would be called with

$ ./script.sh "New Value"

The output would be

New Value,Some Value

To provide a default value for a variable, you may do

variable="$1:-Old Value"

Using this in the above script, the output will say Old Value,Some Value if the script is not called with any command line arguments.

The following short script does proper command line parsing of three command line flags, -a, -b and -c. The flags -a and -b takes an argument while -c does not. It uses three variables, var_a, var_b and var_c, that have default values that may be overridden by using the command line flags.

At the end, the script displays the values of these variables, and also displays what else might have been given on the command line.

#!/bin/sh

var_a=12
var_b="yellow"
var_c=0

while getopts 'a:b:c' opt; do
 case "$opt" in
 a) var_a=$OPTARG ;;
 b) var_b=$OPTARG ;;
 c) var_c=1 ;;
 *) echo 'command line parsing error' >&2
 exit 1
 esac
done

shift $(( OPTIND - 1 ))

printf 'var_a = %snvar_b = %snvar_c = %sn' 
 "$var_a" "$var_b" "$var_c"

if [ "$#" -gt 0 ]; then
 echo 'Other operands:'
 printf '%sn' "$@"
fi

Running it a few times:

$ ./script.sh
var_a = 12
var_b = yellow
var_c = 0

$ ./script.sh -b "green tea" "hello world"
var_a = 12
var_b = green tea
var_c = 0
Other operands:
hello world

$ ./script.sh -c my other car is a cdr
var_a = 12
var_b = yellow
var_c = 1
Other operands:
my
other
car
is
a
cdr

$ ./script.sh -a -d
var_a = -d
var_b = yellow
var_c = 0

$ ./script.sh -a
./script.sh[15]: -`a' requires argument
command line parsing error

$ ./script.sh -a "boo!" "help!" -c
var_a = boo!
var_b = yellow
var_c = 0
Other operands:
help!
-c