How can I loop over zsh array and use index and value in other commands?

Question

$ zsh --version
zsh 5.8 (x86_64-apple-darwin19.6.0)
$ tmux -V
tmux 3.2a

I am automating a remote server monitoring dashboard in tmux via zsh script.

Store the multiline output of a command as an array in zsh: (WORKS)

$ server_name_array=( $( aws ec2 describe-instances... ) )
$ declare -p server_name_array
typeset -a server_name_array=( name1 name2 name3 )

Then want to use both the index and value of each array item in my tmux command: (DOES NOT WORK)

$ for i in "${!server_name_array[@]}"; \
do \
  tmux send-keys -t '=server:=servers.<server_name_index>' 'ssh <server_name_value> -t "<my-remote-command>"'; \
done;

But I get the following error:

zsh: event not found: server_name_array[@]

I have read this is due to the special ! operator in bash and have tried escaping / unsetting it as suggested to no avail:

$ set +H
$ for index in "${"'!'"server_name_array[@]}"; do echo $index; done;
zsh: bad substitution
$ for index in "${"\!"server_name_array[@]}"; do echo $index; done;
zsh: bad substitution
$ for index in "${"'!'"server_name_array[@]}"; do echo $index; done;
zsh: bad substitution
$ for index in "${"\!"server_name_array[@]}"; do echo $index; done;
zsh: bad substitution
$ for index in "${!server_name_array[@]}"; do echo $index; done;
zsh: event not found: server_name_array[@]
$ for index in "${\!server_name_array[@]}"; do echo $index; done;
zsh: bad substitution

What am I doing wrong?

UPDATE:

Here is my script invoked via .sh file:

$ ls -ahl /usr/local/bin/server_mon
lrwxr-xr-x  1 <user>  admin    48B <date> /usr/local/bin/server_mon -> ~/scripts/server_mon.sh

#!/bin/sh

set -euC

cd <project-directory>

# our main function
attach() {
    [ -n "${TMUX:-}" ] &&
        tmux switch-client -t '=server' ||
        tmux attach-session -t '=server'
}

# attach to server if it already exists
if tmux has-session -t '=server' 2> /dev/null; then
    attach
    exit 0
fi

# start a named session called server
tmux new-session -d -s 'server' -n 'local'; \

# new tmux servers window
tmux new-window -d -t '=server' -n 'servers'; \

# store the names of our server instances in an array
server_name_array=( $( aws ec2 describe-instances ... ) )
declare -p server_name_array
# typeset -a server_name_array=( name1 name2 name3 )
server_name_array_length=${#server_name_array[@]:1}

# create split panes for number of servers (n-1)
for i in "${server_name_array[@]:1}"; do tmux split-window -t '=server:=servers' -d; done;
# select an even vertical layout
tmux select-layout -t '=server:=servers' even-vertical;

# vvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
# HERE IS WHAT I AM TRYING TO DO
# vvvvvvvvvvvvvvvvvvvvvvvvvvvvvv

# Loop over ZSH array of server names, and send ssh commands containing server names to panes via the array index
for i in "${!server_name_array[@]}"; 
do
    # tmux send-keys -t '=server:=servers.<server_name_index>' 'ssh <server_name_value> -t "<my-remote-command>"';
    tmux send-keys -t '=server:=servers.${$i}' 'ssh ${server_name_array[$i] -t "sudo su;"' Enter; 
done;

"What am I doing wrong?" -- in my opinion, trying to write a program that both bash and zsh can run. Pick one or the other. — glenn jackman
– glenn jackman, Commented Apr 19, 2022 at 19:28
@glennjackman My script has #!/bin/sh at the top. I'm using zshell in terminal. Testing these command I am using the terminal. When I run the script aliased to <script.sh>, is ZSH running it or BASH? — eschie
– eschie, Commented Apr 19, 2022 at 19:56
clearly zsh is, as you get the zsh error. Show the content of the script and especially show exactly how you invoke it. — glenn jackman
– glenn jackman, Commented Apr 19, 2022 at 19:58
@eschie If you're using a generic #!/bin/sh shebang, you shouldn't use any non-POSIX features (like arrays) at all, because you aren't in control of which shell the scripts runs under. Do not worry about figuring out what /bin/sh is on your system, because that's subject to change. If you want to use non-POSIX features, you should pick a specific shell, use a shebang that specifies that shell, and then use that shell's syntax. — Gordon Davisson
– Gordon Davisson, Commented Apr 19, 2022 at 20:17

Philippe · Accepted Answer · 2022-04-19 20:17:10Z

4

Following script produces same result in bash and zsh :

declare -a server_name_array=(a b c)

test "$ZSH_VERSION" && c=1 || c=0

for ((i=0; i<${#server_name_array[@]}; i++)); do
    echo $i "${server_name_array[i+c]}"
done

output :

$ bash test.sh
0 a
1 b
2 c
$ zsh  test.sh
0 a
1 b
2 c

answered Apr 19, 2022 at 20:17

Philippe

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3 Comments

Mehrshad Khansarian Over a year ago

I'm on zsh 5.8.1 (x86_64-apple-darwin21.0) and I don't get the same result.

Philippe Over a year ago

@MehrshadKhansarian I get same result on zsh 5.9 (x86_64-apple-darwin22.1.0). Can you post your result ?

Mehrshad Khansarian Over a year ago

I am sorry, I was mistaken. I hadn't noticed the i+c index, which practically starts indexing at 1 on zsh and 0 on bash.

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