How to use multiple hostnames in single bash variable?

Question

Working script for single host

I sourced the following bash scripts inside .bashrc and is working fine with single hostname host1. I can do scp, rsync and other remote commands without any problem. But I want to use it for multiple hostnames eg. host1, host2, host3.

HPC_HOST=${HPC_HOST:-host1}

lastarg() {
    # get the last argument
    for last; do true; done; echo $last;
}

hpc() {
    HERE="~${PWD#$HOME}"
    ssh -t $HPC_HOST "cd $HERE; bash";
}

scp_to_hpc() {
    # Usage: scp_to_hpc files
    # Purpose: will copy file to crysden:$(pwd)/file
    #hpc_mkcwd
    HERE="~${PWD#$HOME}"
    scp $@ $HPC_HOST:$HERE
}

Current Solution

Currentlty I created three copies of the same script and modified the function names accordingly with respect to host name.

Expected Solution

I expect there must be a way to call the multiple hostname in the above script. and execute the commands with anyhost.( may be we need to define function varaible as well for host name.

I also apreciate the possible ideas to use multiple host in the above bash script.

Do you mean you want to run the same command on three hosts in one go, or just generalize the script so it doesn't hard-code `host1`? — tripleee, Jul 19 '21 at 08:34
As an aside, an unquoted `$@` is basically always a bug; it will break if you have arguments which contain spaces. In general, try http://shellcheck.net/ before asking for human assistance. — tripleee, Jul 19 '21 at 08:35
@tripleee Thanks for your suggestion regarding `$@`. I will look into it. Currently, I managed to solved my problem by putting everything inside the heredoc and changed all functions name into a variable, e.g `scp_to_hpc` into `scp_to_${hpc}`. So for every host it creates separate files. Sorry for the late reply. And thanks for your suggestion. — sai, Aug 10 '21 at 04:43

Shaqil Ismail · Answer 1 · 2021-07-19T08:33:08.093

You can use a dictionary in bash, have multiple keys and you set the value, when you want to use a specific key, then you can retrieve this.

To create a dictionary declare -A test_var

Add key/value string literals without quote test_var[key1]=value1

Add key/value string literals with quote test_var['key2']='value2'

Add key/value pair using bash variables

another_key_var='key3'
another_value_var='value3'
test_var[$another_key_var]=$another_value_var

to retrieve key-value pairs in bash

echo ${test_var[key1]}
echo ${test_var[key2]}
echo ${test_var[$another_key_var]}

Update an Existing Key-Value in a Dictionary in Bash `test_var[key1]='another_value1'

Check if a Key Exists in a Dictionary in Bash

if [ -v test_var[key1] ]; then
    echo "key1 exists in a dictionary"
fi

if [ ! -v test_var[key2] ]; then
    echo "key2 does not exists in a dictionary"
fi

Remove a Key-Value Pair from a Dictionary in Bash

unset test_var[key1]
unset test_var['key2']
unset test_var[$another_key_var]

Iterate a Dictionary in Bash

for key in "${!test_var[@]}"; do
    echo "$key ${test_var[$key]}"
done

Perhaps note that associative arrays are a Bash 4+ feature, though, which means e.g. MacOS users still get a too old Bash version out of the box. — tripleee, Jul 19 '21 at 08:31
@Shaqil Ismail, thanks a lot for your idea. I will look in this way while implementing the script. Currently, I managed to write a working script, but later I will implement it. Sorry for the late response, and thanks a lot for your suggestions. — sai, Aug 10 '21 at 04:47

How to use multiple hostnames in single bash variable?

Working script for single host

Current Solution

Expected Solution

1 Answers1