Getopts parsing command line parameters for unixshell learning

The getopts parsing command line parameter getopts command is built in shell. you can get the valid command line parameters specified by a single character. each character has a & amp; lsquo; -& amp; rsquo; No. or & amp; lsquo; + & amp; rsquo; No. To put it simply, for example, run the command: iptabl unix shell to learn the getopts parsing command line parameter getopts command is built-in in shell, you can get the valid command line parameter specified by a single character, A single character has a '-' or '+. To put it simply, run the following command: iptables-t nat-a postrouting-p tcp-o eth0-s 192.168.2.0/24-j SNAT -- to public_ip it implements the function of converting an intranet ip address to A public ip address to access the Internet, however, how can we parse so many parameters? getopts is to parse such parameters. Therefore, getopts is a very practical tool. it helps you easily parse command line parameters when you write scripts. but how does it parse it, if the script provides the command line parameter-s 5-m 10-d 2-p my_shell, use getopts: s: m: h: d: p indicates that if ":" is added before each switch for the specified item s, m, d, and p, a parameter is required for this toggle. For details, see the code my_shell.sh. it implements the function of converting all parameters such as daily hours, minutes, and seconds to seconds: click (here) fold or open SECS = 0 MINUTES = 0 HOURS = 0 DAYS = 0 PROCESS = 0 while getopts: s: m: h: d: p TIMED 2>/dev/NullDC case $ TIMED in s) SECS = $ OPTARG; m) (MINUTES = $ OPTARG * 60); h) (HOURS = $ OPTARG * 3600); d) (DAYS = $ OPTARG * 86400); p) PROCESS = $ OPTARG ;;\?) Usage exit; esacdone (TOTALSECS = $ SECS + $ MINUTES + $ HOURS + $ DAYS) echo "total seconds: $ TOTALSECS" run the command at this time: bash my_shell.sh-s 20-m 3-h 5-d 8-p my_shell, you can see the result of parsing parameters after running the command.