Bash 4.0.0中$ @未绑定变量的解决方法？

Question

In specifically Bash version 4.0.0 , is there any way to work around the use of an empty $@ raising an unbound variable error when set -u is enabled?

Consider the following:

#!/usr/bin/env bash-4.0.0-1

set -xvu

echo "$BASH_VERSION"
echo "${BASH_VERSINFO[@]}"

main () {
  printf '%q\n' "${@:-}"
}

main "${@:-}"

Gives me the following output when I provide an empty set of arguments:

neech@nicolaw.uk:~ $ ./test.sh

echo "$BASH_VERSION"
+ echo '4.0.0(1)-release'
4.0.0(1)-release
echo "${BASH_VERSINFO[@]}"
+ echo 4 0 0 1 release x86_64-unknown-linux-gnu
4 0 0 1 release x86_64-unknown-linux-gnu

main () {
  printf '%q\n' "${@:-}"
}

main "${@:-}"
./test.sh: line 12: $@: unbound variable

I only see this behaviour in Bash version 4.0.0 .

I was hoping that using variable substitution ${@:-} would allow me to work around this, but it seems not.

Is there a way to work around this?

Answer 1

$@ , $* are special variables so should always be defined it's a bug

https://unix.stackexchange.com/questions/16560/bash-su-unbound-variable-with-set-u

a workaround, maybe:

set +u
args=("$@")
set -u

main "${args[@]}"

or maybe also

main "${@:+$@}"

Answer 2

Why not do error handling on your own? This way you can control exactly what happens when an exception is encountered, for instance return a custom exit code and message for that error, rather than be confined to some predefined behavior.

function log_error                                                          
{                                                                           
    [[ $# -ne 1 ]] && return 1                                              

    typeset msg="$1"                                                        
    typeset timestamp=$(date "+%F %T")                                      

    echo "[${timestamp}] [ERROR] - $msg " >&2                               
}

if [[ -z "$BASH_VERSION" ]]                                                 
then                                                                        
    log_error "BASH VERSION is not set"                                     
    exit 1                                                                  
fi