I was digging through mysql_safe (trying to add some options) and I came across

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Asked: May 26, 20262026-05-26T04:26:29+00:00 2026-05-26T04:26:29+00:00

I was digging through mysql_safe (trying to add some options) and I came across

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I was digging through mysql_safe (trying to add some options) and I came across this bash scripting technique they use to assign variables from the Launch Agent:
com.mysql.mysqld.plist (I’m on a mac).

Now mysqld_safe doesn’t know it’s being invoked by LaunchCtl, so I assume any options are converted by LaunchCtl into command line arguments, but I found this sytnax intruiging.
Anyone know how this works?

I understand the basics of Case/Switch in Bash:

case "$myval" in
  switch1) do something;;
  switch2) do something;;
        *) do whatever fallthrough logic;;
esac

with the default fall through using *
In the script chunk below, the arg value is:
“–basedir=” or “–datadir=” or “–pid-file=”, etc
But WHAT IS UP WITH THE * in there?
Is that a Regular Expression in Switch Statement??
WITH A BACKREFERENCE?

for arg do
  # the parameter after "=", or the whole $arg if no match
  val=`echo "$arg" | sed -e 's;^--[^=]*=;;'`
  # what's before "=", or the whole $arg if no match
  optname=`echo "$arg" | sed -e 's/^\(--[^=]*\)=.*$/\1/'`
  # replace "_" by "-" ; mysqld_safe must accept "_" like mysqld does.
  optname_subst=`echo "$optname" | sed 's/_/-/g'`
  arg=`echo $arg | sed "s/^$optname/$optname_subst/"`
  arg=`echo $arg | sed "s/^$optname/$optname_subst/"`
  case "$arg" in
    # these get passed explicitly to mysqld
    --basedir=*) MY_BASEDIR_VERSION="$val" ;;
    --datadir=*) DATADIR="$val" ;;
    --pid-file=*) pid_file="$val" ;;
    --plugin-dir=*) PLUGIN_DIR="$val" ;;
    --user=*) user="$val"; SET_USER=1 ;;
    ...
    ...
    *)
      if test -n "$pick_args"
      then
        append_arg_to_args "$arg"
      fi
      ;;
  esac