Syntax error in redirection is not identified

[lijh8]

Hi,

Syntax error in redirection is not identified.

$ cat hello.sh 
#!/bin/bash

shopt -s expand_aliases
alias echo='echo "$BASH_SOURCE:$LINENO:$FUNCNAME:"'

main1() {
        local a b c d

        a=20
        b=30
        c=`expr $a + $b 2 > /dev/null` # should be 2>
        d=$?
        test $d -eq 0 -o $d -eq 1 && echo "$c" || echo "error: $a + $b"
}

main1
$ 

$ shellcheck hello.sh; bash hello.sh; 

In hello.sh line 11:
        c=`expr $a + $b 2 > /dev/null` # should be 2>
          ^--------------------------^ SC2006 (style): Use $(...) notation instead of legacy backticks `...`.
           ^--^ SC2003 (style): expr is antiquated. Consider rewriting this using $((..)), ${} or [[ ]].

Did you mean: 
        c=$(expr $a + $b 2 > /dev/null) # should be 2>

For more information:
  https://www.shellcheck.net/wiki/SC2003 -- expr is antiquated. Consider rewr...
  https://www.shellcheck.net/wiki/SC2006 -- Use $(...) notation instead of le...
expr: syntax error: unexpected argument ‘2’
hello.sh:13:main1: error: 20 + 30
$ 

$ cat /etc/os-release | grep PRETTY_NAME
PRETTY_NAME="Debian GNU/Linux trixie/sid"
$ 

$ shellcheck --version
ShellCheck - shell script analysis tool
version: 0.10.0
license: GNU General Public License, version 3
website: https://www.shellcheck.net
$