The shell script uses two bars to receive external parameters

First , The effect is this ：
Can handle both short options （-） You can also handle long options （--）

[[email protected] shell]$ ./demo.sh --help
sqoop The program starts running ： demo.sh
Usage: ./demo.sh [options]
 
Options:
 --append, -a:      Append import （ The default is append mode ）
 --overwrite, -o:   Overlay import  
 
 --method, -m:     single- One day import 
                   interval- Interval import 
                   all- Full table import 
 
 --date, -d:        One day import , Some date data （ The format is yyyymmdd）
 
 --startdate, -s:   Interval import , Start date 
 --enddate, -e:     Interval import , End date 
 
 --help, -h          help 

shell There is a very simple way for scripts to take external parameters , Use... In scripts $0,$1,$2... Refers to the first parameter passed in when executing a script （$0 It's the script name ）.

however , It's not elegant after all ,

Another way shell Use... In scripts getopts command , Only short options are allowed （eg：-d,-s,-h）, Very convenient , Relatively simple , You can search for it yourself .

But if you want to achieve the above effect, support both long options and short options （eg：--date,-d,--startdate,-s,--help,-h）,

You can only use getopt The command ：
 

#  Define Command Execution Options 
#  Parameters are not followed by a colon （a） Indicates that no parameter is followed  eg:-a,--append
#  The parameter is followed by a colon （a:） It means that parameters must be followed  eg:-d 20201224,--date 20201224
#  Parameters are followed by two colons （a::） Indicates whether the following parameters can be connected or not 
if ! ARGS=$(getopt -o aom:d:s:e:h --long append,overwrite,method:,date:,startdate:,enddate:,help -n "$0" -- "[email protected]"); then
    echo "Terminating..."
    echo -e "Usage: ./$SCRIPT_NAME [options]\n"
    echo -e "Options:\n --append, -a:      Append import （ The default is append mode ）\n --overwrite, -o:   Overlay import  \n\n --method, -m:     single- One day import \n                   interval- Interval import \n                   all- Full table import \n\n --date, -d:        One day import , Some date data （ The format is yyyymmdd）\n\n --startdate, -s:   Interval import , Start date \n --enddate, -e:     Interval import , End date \n\n --help, -h          help "
    exit 1
fi
 
#  Assign normalized command line parameters to positional parameters （$1,$2,...)
# The -- ensures that whatever options passed in as part of the script won't get interpreted as options for set, but as options for the command denoted by the $progname variable.
eval set -- "${ARGS}"
 
#  Accept Execution Options ; Assign a value to a variable 
while true; do
  case "$1" in
    -a|--append)
      mode='append'
      shift
      ;;
    -o|--overwrite)
      mode='overwrite'
      shift
      ;;
    -m|--method)
      method=$2
      shift 2
      ;;
    -d|--date)
      date=$2
      shift 2
      ;;
    -s|--startdate)
      startdate=$2
      shift 2
      ;;
    -e|--enddate)
      enddate=$2
      shift 2
      ;;
    --)
      shift
      break
      ;;
    -h|--help)
      echo -e  "Usage: ./$SCRIPT_NAME [options]\n"
      echo -e  "Options:\n --append, -a:      Append import （ The default is append mode ）\n --overwrite, -o:   Overlay import  \n\n --method, -m:     single- One day import \n                   interval- Interval import \n                   all- Full table import \n\n --date, -d:        One day import , Some date data （ The format is yyyymmdd）\n\n --startdate, -s:   Interval import , Start date \n --enddate, -e:     Interval import , End date \n\n --help, -h          help "
      exit 0
      ;;
    ?)
      echo "missing options, pls check!"
      exit 1
      ;;
  esac
done