sh version : 1.14.7
#!/bin/sh
cpu_to_eth1=10
cpu_to_eth2=20
cpu_to_eth3=30
cpu_to_eth4=40
i=0
for i in 1 2 3 4
do
echo "value of the $i th varible is $cpu_to_eth$i"
done
it is not working properly,the output should be
value of the 1 th varible is 10
value of the 2 th varible is 20
value of the 3 th varible is 30
value of the 4 th varible is 40
Without requiring bash:
#!/bin/sh
cpu_to_eth1=10
cpu_to_eth2=20
cpu_to_eth3=30
cpu_to_eth4=40
for i in 1 2 3 4; do
eval echo "value of the $i th varible is "$"cpu_to_eth$i"
done
This should work in any POSIX shell (e.g. in dash, the default shell in Ubuntu).
The point is that you need two evaluations (for an indirect evaluation):
$i to get the name of the variable (cpu_to_eth$i)cpu_to_eth$i to get its actual valueThe second-order evaluation needs a separate eval (or a bash-ism)
eval another_var=\$"cpu_to_eth$i"With bash, it's more appropriate to use an array here, rather than have multiple variables.
Example of an array:
cpu_to_eth_arr=( 10 20 30 40 )
for i in "${cpu_to_eth_arr[@]}"
do
echo "$i"
done
Another way, using an associative array:
cpu_to_eth[1]=10
cpu_to_eth[2]=20
cpu_to_eth[3]=30
cpu_to_eth[4]=40
for i in "${!cpu_to_eth[@]}"
do
echo "value of the $i th varible is ${cpu_to_eth[$i]}"
done
Using bash you can perform the Shell parameter expansion:
#!/bin/bash
cpu_to_eth1=10
cpu_to_eth2=20
cpu_to_eth3=30
cpu_to_eth4=40
i=0
for i in 1 2 3 4
do
val=cpu_to_eth${i} # prepare the variable
echo value of the $i th varible is ${!val} # expand it
done
#!/bin/sh to #!/bin/bash.
$cpu_to_eth, followed by$i. just as you would expect.bash?