pass function parameter as name instead of as a string

Question

With this function:

repr() {
    declare -p $1 | cut -d '=' -f 2- > /tmp/.repr
    $1=$(</tmp/.repr)
    rm /tmp/.repr
}

It gives an error message, when I write:

repr test

This see the argument as string:

repr() {
    declare -p 'test' | cut -d '=' -f 2- > /tmp/.repr
    'test'=$(</tmp/.repr)
    rm /tmp/.repr
}

And not as name:

repr() {
    declare -p test | cut -d '=' -f 2- > /tmp/.repr
    test=$(</tmp/.repr)
    rm /tmp/.repr
}

How can I solve the problem?

Instead of typeset -p | cut use printf %q (see the update to my A to your previous Q. Eg. repr() { repr() { printf -v "$1" %q "$2"; } to use as repr varname string: repr q "e's f"; echo "$q" => e\'s\ f. — , Mar 13 '20 at 16:18
In general, you can pass variable by names via references (declare -n): set_to_13(){ declare -n v=$1; v=13; }; set_to_13 var; echo "$var" => 13. — , Mar 13 '20 at 16:20
Be aware that the nameref persists: if you unset v it will unset var and leave v defined. You erase the nameref with unset -n v. — Paul_Pedant, Mar 13 '20 at 17:02
printf -v bar %q "$foo" in the function is read like: printf -v 'bar' %q "$foo", but despite this, it continues to work. Thank you very much — Riccardo La Marca, Mar 13 '20 at 17:46
@Paul_Pedant, no need to explicitly unset the nameref if it's just used inside that function (declare inside a function makes it local). — ilkkachu, Mar 13 '20 at 18:00
See also: Is it possible to print the content of the content of a variable with shell script? (indirect referencing), get environment variable by variable name?, Use a variable reference “inside” another variable — ilkkachu, Mar 13 '20 at 18:03
@ilkkachu Didn't know that, but it is pretty mucky. local -n also declares a nameref. declare -g -n makes the reference global. local - gives a function a local copy of the shell args that it can modify. Too many special rules around! — Paul_Pedant, Mar 13 '20 at 19:54
I am confused. What are you trying to do? Edit the question to give a simple minimal But less abstract example. — ctrl-alt-delor, Mar 13 '20 at 20:00
https://stackoverflow.com/questions/13716607/creating-a-string-variable-name-from-the-value-of-another-string — s3n0, Mar 13 '20 at 22:57

pass function parameter as name instead of as a string

0 Answers0