golang编程之获取命令行参数及环境变量

    我们写习惯了C代码，都知道了解析输入参数argc argv，获取环境变量env,常见的C语言main函数有：

    int main(int argc,char* argv[],char** envp)

    我们首先给出C语言的获取命令行参数和环境变量的代码：  

manu@manu-hacks:~/code/c/self/env$ cat env.c

#include<stdio.h>
#include<stdlib.h>


int main(int argc,char* argv[],char** envp)
{
    int i;
    printf("there are %d input param\n",argc);
    printf("they are :\n");
    for(i = 0 ; i < argc ; i++)
    {
        printf("%s\n",argv[i]);
    }

    printf("env LIST--------------------------------------\n");
    char **p = envp;
    for(;*p != NULL;p++)
    {
        printf("%s\n",*p);
    }
    return 0;
}

    golang自然也可以做到，获取命令行参数，获取环境变量。

manu@manu-hacks:~/code/go/self$ godoc os Args
PACKAGE DOCUMENTATION

package os
    import "os"



VARIABLES

var Args []string
    Args hold the command-line arguments, starting with the program name.

    我们先写一个简单的获取命令行参数的go 程序：   

manu@manu-hacks:~/code/go/self$ cat sum.go
package main
import "fmt"
import "os"
import "strconv"


func main() int{
    arg_num := len(os.Args)
    fmt.Printf("the num of input is %d\n",arg_num)

    fmt.Printf("they are :\n")
    for i := 0 ; i < arg_num ;i++{
        fmt.Println(os.Args[i])
    }

    sum := 0
    for i := 1 ; i < arg_num; i++{
        curr,err := strconv.Atoi(os.Args[i])
        if(err != nil){
            fmt.Println("error happened ,exit")
            return 1
        }
        sum += curr
    }

    fmt.Printf("sum of Args is %d\n",sum)
    return 0
}

输出如下：

manu@manu-hacks:~/code/go/self$ ./sum  1 2 4
the num of input is 4
they are :
./sum
1
2
4
sum of Args is 7
manu@manu-hacks:~/code/go/self$ ./sum  1 2 4 f 5
the num of input is 6
they are :
./sum
1
2
4
f
5
error happened ,exit

    另外一个方面是如何获取环境变量。对于C而言，直接就是 之际而言os中也有获取环境变量的函数：

FUNCTIONS

func Environ() []string
    Environ returns a copy of strings representing the environment, in the
    form "key=value".

func Getenv(key string) string
    Getenv retrieves the value of the environment variable named by the key.
    It returns the value, which will be empty if the variable is not
    present.

    有了这个，就简单了。写了个简单的例子：  

manu@manu-hacks:~/code/go/self$ cat env.go
package main
import "fmt"
import "os"

func main(){

    environ := os.Environ()
    for i := range environ {
        fmt.Println(environ[i])
    }
    fmt.Println("------------------------------------------------------------\n")
    logname := os.Getenv("LOGNAME")
    fmt.Printf("logname is %s\n",logname)
}

    输出如下：

manu@manu-hacks:~/code/go/self$ go run env.go
SSH_AGENT_PID=2331
GPG_AGENT_INFO=/tmp/keyring-5CkALe/gpg:0:1
TERM=xterm
SHELL=/bin/bash
。。。

------------------------------------------------------------

logname is manu

参考文献
1 Package os