is there a clean, concise way to push/pop bash verbose and xtrace options for a funtion?

Question

(Linux bash 4.1.2) I have a bash function calling another function. The low level function wants to have -xv set for debugging, but I don't want it to mess with the values of x and v in the parent function. I.e. I want the child function to push -xv, then restore the previous setting on return. E.g.:

function outer(){ echo starting; inner; echo done; }
function inner(){
    set -xv
    echo inside
    set +xv
  }
outer

This works if the setting in outer is default; otherwise it forces +xv in the rest of outer's code. I can imagine some very messy script that parses BASHOPTS, but it seems like there should be a better way?

score 3 · Accepted Answer · answered Apr 02 '19 at 17:54

If you don't need to share the outside code's environment or modify variables from outside within inside, you can launch a subprocess with ( inner )

function outer(){ echo starting; inner; echo done; }
function inner(){
    (
        set -xv
        echo inside
    )
}
outer

Note that since you are executing in a subshell, you don't need to unset the x and v.

You can also simply wrap the call to inner in outer without modifying inner:

function outer(){ echo starting; ( inner ); echo done; }

You can find more information here about subshells and variable scopes. https://www.tldp.org/LDP/abs/html/subshells.html

score 0 · Answer 2 · answered Apr 02 '19 at 18:10

0

  local save=$-; set -x
  ...
  set +x -$save

answered Apr 02 '19 at 18:10

Mischa

2,240
20
18

This won't work if `save` contains any read-only options like `i`. – chepner Apr 02 '19 at 18:42
Within a shell script, "-i" has been removed from $-. – Mischa Aug 02 '19 at 23:20
1

`i` is not the only problematic character. – chepner Aug 03 '19 at 15:19

is there a clean, concise way to push/pop bash verbose and xtrace options for a funtion?

2 Answers2