Go parsing command line parameter flag package

Catalog

One 、 Get command line parameters

Two 、flag Basic use of package

1、flag Parameter type

2、 Define the command line flag Parameters

3、flag Other functions

4、flag Package complete example

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Go Language built in flag The package implements the parsing of command line parameters ,flag Packages make developing command-line tools easier .

One 、 Get command line parameters

os.Args： If you simply want to get command line arguments , It can be used like the following code example os.Args To get command line arguments .

package main

import (
    "fmt"
    "os"
)

//os.Args demo
func main() {
    //os.Args It's a []string
    if len(os.Args) > 0 {
        for index, arg := range os.Args {
            fmt.Printf("args[%d]=%v\n", index, arg)
        }
    }
}

Execute the above code go build -o "args_demo" After the compilation , perform ：

$ ./args_demo a b c d
args[0]=./args_demo
args[1]=a
args[2]=b
args[3]=c
args[4]=d

os.Args Is a string slice that stores command line parameters , Its first element is the name of the execution file .

Two 、flag Basic use of package

import flag

1、flag Parameter type

flag The command line parameter types supported by the package are bool、int、int64、uint、uint64、float float64、string、duration.

flag Parameters	Valid values
character string flag	Legal string
Integers flag	1234、0664、0x1234 Other types , It can also be negative .
Floating point numbers flag	Legal floating point number
bool type flag	1, 0, t, f, T, F, true, false, TRUE, FALSE, True, False.
Period of time flag	Any legal time period string . Such as ”300ms”、”-1.5h”、”2h45m”. Legal units include ”ns”、”us” /“µs”、”ms”、”s”、”m”、”h”.

2、 Define the command line flag Parameters

There are two common definitions of the command line flag Parameter method .

flag.Type()

The basic format is as follows ：

flag.Type(flag name ,  The default value is ,  Help information )*Type

For example, we want to define names 、 Age 、 There are three command line parameters for marriage , We can define... As follows ：

name := flag.String("name", " Zhang San ", " full name ")
age := flag.Int("age", 18, " Age ")
married := flag.Bool("married", false, " marriage ")
delay := flag.Duration("d", 0, " The time interval ")

It should be noted that , here name、age、married、delay Are pointers to corresponding types .

flag.TypeVar()

The basic format is as follows ： flag.TypeVar(Type The pointer , flag name , The default value is , Help information ) For example, we want to define names 、 Age 、 There are three command line parameters for marriage , We can define... As follows ：

var name string
var age int
var married bool
var delay time.Duration

flag.StringVar(&name, "name", " Zhang San ", " full name ")
flag.IntVar(&age, "age", 18, " Age ")
flag.BoolVar(&married, "married", false, " marriage ")
flag.DurationVar(&delay, "d", 0, " The time interval ")

flag.TypeVar() Get the variable of , Not a pointer can be used directly

remarks ： Approved above flag.Type(),flag.TypeVar() You can obtain command line parameters in both ways , Must be used after obtaining flag.Parse() analysis

flag.Parse()

Define the command line in two ways flag After the parameter , You need to call flag.Parse() To parse the command line parameters .

The supported command line parameter formats are as follows ：

-flag xxx （ Use spaces , One - Symbol ）
--flag xxx （ Use spaces , Two - Symbol ）
-flag=xxx （ Use equal sign , One - Symbol ）
--flag=xxx （ Use equal sign , Two - Symbol ）

among , Parameters of boolean type must be specified with equal sign .

Flag Resolution in the first non flag Parameters （ Single ”-“ No flag Parameters ） Stop before , Or in the Terminator ”–“ Stop after .

3、flag Other functions

flag.Args()  Return other parameters after command line parameters , With []string type 
flag.NArg() // Returns the number of other parameters after the command line parameters 
flag.NFlag() // Returns the number of command line arguments used 

4、flag Package complete example

func main() {
    // Define the command line arguments 1
    var name string
    var age int
    var married bool
    var delay time.Duration
    
    flag.StringVar(&name, "name", " Zhang San ", " full name ")
    flag.IntVar(&age, "age", 18, " Age ")
    flag.BoolVar(&married, "married", false, " marriage ")
    flag.DurationVar(&delay, "d", 0, " The interval of delay ")

    // Parsing command line arguments 
    flag.Parse()
    fmt.Println(name, age, married, delay)
   
     // Return other parameters after command line parameters , This is an array 
    fmt.Println(flag.Args())
    
    // Returns the number of command line arguments used 
    fmt.Println(flag.NFlag())
    
    // Returns the number of other parameters after the command line parameters 
    fmt.Println(flag.NArg())
}

Command line usage ：

1） Command line parameters use prompt ：

$ ./flag_demo -help
Usage of ./flag_demo:
  -age int
         Age  (default 18)
  -d duration
         The time interval 
  -married
         marriage 
  -name string
         full name  (default " Zhang San ")

2） Use the command line normally flag Parameters ：

$ ./flag_demo -name pprof --age 28 -married=false -d=1h30m
pprof 28 false 1h30m0s
[]
0
4

3） Use non flag Command line arguments ：

$ ./flag_demo a b c
 Zhang San  18 false 0s
[a b c]
3
0