In /usr/bin/su-to-root line 4:
. /etc/su-to-rootrc
  ^---------------^ SC1091: Not following: /etc/su-to-rootrc was not specified as input (see shellcheck -x).


In /usr/bin/su-to-root line 8:
. ~/.su-to-rootrc
  ^-------------^ SC1090: Can't follow non-constant source. Use a directive to specify location.


In /usr/bin/su-to-root line 23:
  printf "$txt" "$@"
         ^----^ SC2059: Don't use variables in the printf format string. Use printf '..%s..' "$foo".


In /usr/bin/su-to-root line 27:
   getent passwd $1 | cut -f7 -d:
                 ^-- SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
   getent passwd "$1" | cut -f7 -d:


In /usr/bin/su-to-root line 55:
privid=$(id -u $PRIV)
               ^---^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
privid=$(id -u "$PRIV")


In /usr/bin/su-to-root line 66:
    SHELL=`eshell $PRIV`
          ^------------^ SC2006: Use $(...) notation instead of legacy backticked `...`.
                  ^---^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
    SHELL=$(eshell "$PRIV")


In /usr/bin/su-to-root line 67:
    case $SU_TO_ROOT_SU in
         ^------------^ SC2153: Possible misspelling: SU_TO_ROOT_SU may not be assigned, but SU_TO_ROOT_X is.


In /usr/bin/su-to-root line 68:
      sux)  suname=sux; pwuser="$PRIV"; cmd='sux  -p "$PRIV" "$COMMAND"';;
                                            ^--------------------------^ SC2016: Expressions don't expand in single quotes, use double quotes for that.


In /usr/bin/su-to-root line 69:
      sudo) suname=sudo;pwuser="$USER"; cmd='sudo -u "$PRIV" sh -c "$COMMAND"';;
                                            ^-- SC2016: Expressions don't expand in single quotes, use double quotes for that.


In /usr/bin/su-to-root line 70:
      *)    suname=su;  pwuser="$PRIV"; cmd='su   -p "$PRIV" -c "$COMMAND"';;
                                            ^-----------------------------^ SC2016: Expressions don't expand in single quotes, use double quotes for that.


In /usr/bin/su-to-root line 75:
    while ! eval $cmd; do
                 ^--^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
    while ! eval "$cmd"; do


In /usr/bin/su-to-root line 77:
      read ans
      ^--^ SC2162: read without -r will mangle backslashes.

For more information:
  https://www.shellcheck.net/wiki/SC1090 -- Can't follow non-constant source....
  https://www.shellcheck.net/wiki/SC2153 -- Possible misspelling: SU_TO_ROOT_...
  https://www.shellcheck.net/wiki/SC1091 -- Not following: /etc/su-to-rootrc ...