mjhjmtu

I have this bash code:

 local r2g_keep_temp=$(r2g_match_arg "--keep" "$my_args[@]");
 local r2g_multi_temp=$(r2g_match_arg "--multi" "$my_args[@]");

 local r2g_multi=[ "$r2g_multi_temp" || "$r2g_keep_temp" ];

I just want r2g_multi to represent a boolean, if either $r2g_multi_temp or $r2g_keep_temp is defined. How can I do that? The above is syntactically invalid.

On the other hand, this is syntactically valid, but not sure if it's correct:

local r2g_multi=$("$r2g_multi_temp" || "$r2g_keep_temp");

There are no booleans in the shell scripts.

Best simulation for them are integer values.

For example, 0 for true and 1 for false.

[[ -v variable_name ]] will return 1 if the variable_name was not defined or 0 if it was.

Therefore, you can get your desired behavior with this:

// If one of the variables is defined, return value of this command is 0.
[[ -v r2g_keep_temp ]] || [[ -v r2g_multi_temp ]]

// Save the return value of the last command (0 or 1).
local r2g_multi="$?"

Of courese, you can interpret the numbers however you like, I just wanted to demonstrate one example.

By the way,

local r2g_multi=$("$r2g_multi_temp" || "$r2g_keep_temp");

is not the thing that you wish.

1. First the variables r2g_multi_temp and r2g_keep_temp will be replaced by their values.


2. Now the subshell will try to execute the value of the r2g_multi_temp.


3. If by some miracle that value is a valid bash command there are 2 cases:
   
   
   • That command is executed succesfully and its stdout is saved in the r2g_multi.
   
   
   • That command failed and subshell invoked the value of the r2g_multi_temp.
     
     Similar story again, if it is a valid command it will be executed and its stdout will be appended on the possible stdout of the command executed from the value of r2g_keep_temp and everything will be stored in r2g_multi.
   
   

All in all, run away from this :D