[shell]shell脚本传入不固定参数的写法，如--help等

最近在调试一个wifi模块，需要传一些不固定的参数，一下一个参数解析的函数可以搞定这个事情，里面内容好多部分是从一个example中剽窃而来(窃喜)

#!/bin/bash
# writen by aaron.gao at 2017.06.

arg_ssid="ssid-test"
arg_passphrase="passphrase-test"
arg_ifip="192.168.4.1"
arg_stop=""
arg_start=""
arg_help=""

print_help() {
  cat <<EOF
  use $program --ssid=<ssid>

    --ssid=<ssid> - where <ssid> is the name of the AP advertised with the beacon frames. (default:$arg_ssid)
    --passphrase=<passphrase> - where <passphrase> is the password of AP (default:$arg_passphrase)

    --stop  - stop accesspoint
    --start - also start accesspoint
    --help  - prints help screen

EOF
}

parse_arguments() {
  local helperKey="";
  local helperValue="";
  local current="";

  while [ "$1" != "" ]; do
      current=$;
      helperKey=${current#*--};
      helperKey=${helperKey%%=*};
      helperKey=$(echo "$helperKey" | tr '-' '_');
      helperValue=${current#*=};
      if [ "$helperValue" == "$current" ]; then
        helperValue="";
      fi
      #echo "eval arg_$helperKey=\"$helperValue\"";

      eval "arg_$helperKey=\"$helperValue\"";
      shift
  done
}

parse_arguments ${@};

if [ "$arg_help" != "" ]; then
    print_help;
     exit ;
fi

if [ "$arg_stop" == "" ]; then
    kill $(pidof -o %PPID -x $(basename $))
    ./uaputl.exe bss_stop

    ifconfig uap0 down;
    exit
fi

ifconfig uap0 up;

# echo "set ssid and passwd"
./uaputl.exe sys_cfg_ssid $arg_ssid
./uaputl.exe sys_cfg_auth
./uaputl.exe sys_cfg_protocol  #sets WPA2 protocol
./uaputl.exe sys_cfg_wpa_passphrase $arg_passphrase
./uaputl.exe sys_cfg_cipher   #PAIRWISE_CIPHER:AES CCMP GROUP_CIPHER:AES CCMP

# echo "set RF params"
./uaputl.exe sys_cfg_channel   #Set AP primary radio channel to , and
# secondary channel is below.
./uaputl.exe sys_cfg_2040_coex  #enable / BSS coexistence Configuration
./uaputl.exe sys_cfg_11n  0x116e   0xff
./uaputl.exe sys_cfg_rates 0xc 0x12 0x18 0x24 0x30 0x48 0x60 0x6c

# echo "set regulation domain"
./uaputl.exe sys_cfg_80211d state  country DE

if [ "$arg_start" == "" ]; then
  sleep ;
  ./uaputl.exe bss_start

  ifconfig uap0 "$arg_ifip"

fi

exit ;