Try to complete some CLI program with golang…….
Selpg-Go的设计实现与测试报告
实验需求
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通过阅读开发Linux命令行实用程序，使用Go语言重新编码selpg，命名为selpg-go，要求相应输入的结果要与C语言selpg相同输出。
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对selpg程序的介绍：
selpg程序全称为select pages，是一个可以从文本文件输入中选择相应页范围，并实现范围内文本打印输出的命令行程序。-sStartPage和-eEndPage为两个强制参数，分别定义了打印页的起始页码与结束页码。-lLines_Per_Pages和-f为一对互斥参数，前者用相应数量的换行定义一页，后者使用换页符\f定义一页。-dPrinter为可选参数，所接参数为打印机名称，开启输出到打印机执行打印功能。fileName为可选参数，输入文件名则以该文件作为输入，否则从标准输入获取。
实验准备
- 熟练掌握
pflag包的用法，spf13/pflag包的Github地址，能够为CLI程序输入参数进行绑定，初始化。下列函数给定了各项参数的初始化，其中value为其缺省值，shorthand为短参数名称。func BoolVar(p *bool, name string, value bool, usage string) func BoolVarP(p *bool, name, shorthand string, value bool, usage string) func IntVar(p *int, name string, value int, usage string) func IntVarP(p *int, name, shorthand string, value int, usage string)程序接收以下形式的flag赋值操作(短参数a为int类型)：
-a1 -a=1 -a 1 - 关于打印功能的实现，需要开启子进程负责执行打印命令(exec包)，借助到
io.Pipe()实现主进程与子进程之间的Stdin，Stdout，Stderr的交换。// exec包内的相关函数 func Command(name1 string, name2 string, ......string) *Cmd // Cmd对象的方法 func (c *Cmd) StderrPipe()(io.ReaderCloser, error) func (c *Cmd) Run() error func (c *Cmd) Wait() error // io包内的相关函数 func Pipe() (*PipeReader, *PupeWriter) func Copy(dst Writer, src Reader) (write int64, err error)
程序实现
- 参数的设置与输入读取
// Binding pflag to params flag.IntVarP(&startPage, "start_page", "s", -1, "Starting page of selcetion"); flag.IntVarP(&endPage, "end_page", "e", -1, "Ending page of selection"); flag.IntVarP(&pageLen, "page_len", "l", 72, "One page's length"); flag.BoolVarP(&pageType, "page_type", "f", false, "Using format-limit or not"); flag.BoolVarP(&helpFlag, "help_flag", "h", false, "Need help"); flag.StringVarP(&printDest, "print_dest", "d", "", "The Destination file to print"); flag.Parse();var read io.Reader; if sp.file_name == "" { read = os.Stdin; } else { file, err := os.Open(sp.file_name); if err != nil { fmt.Fprintf(os.Stderr, "%s: Error with file \"%s\" opening!", programName, sp.file_name); os.Exit(6); } read = file; defer file.Close(); } - 程序获取相关页码内容，采用了
bufio包相关函数，bufio-doc/* Loop to get target pages */ for pageLength < sp.end_page * leng { str, err := reader.ReadString(targetDelim); if err != nil { break; } pageLength++; store = append(store, str); } /* Check whether the startPage is greater than total Page num */ if pageLength <= (sp.start_page-1) * leng { fmt.Fprintf(os.Stderr, "%s: StartPage(%d) is greater than total pages num(%.0f), no output...\n", programName, sp.start_page, math.Ceil(float64(pageLength)/float64(leng))); fmt.Printf("%s: Done\n", programName); os.Exit(7); } - 打印功能的实现，此处涉及主进程获取相关页内容输入到子进程的stdin，与子进程的stderr返回给主进程打印(如找不到打印机错误)。
/* Printer Destination Output */ if sp.print_dest != "" { cmd := exec.Command("lp", fmt.Sprintf("-d%v", sp.print_dest)); piper, pipew := io.Pipe(); stderr,_ := cmd.StderrPipe(); go func() { defer pipew.Close(); io.Copy(pipew, stderr); }() cmd.Stdin = strings.NewReader(targetBuf); cmd.Run(); io.Copy(os.Stderr, piper); defer bufio.NewWriter(os.Stderr).Flush(); cmd.Wait(); }
程序测试
- 通过编写
selpg-go-test.sh，分别从：输入文件或stdin，换行模式，换页模式，打印模式测试本程序的输出是否正常。# Test Shell-Program for selpg-go # 1. \n mode, normal file input and stdin input echo "Case 1==================================================" selpg-go -s1 -e1 ../test.txt echo "Case 2==================================================" selpg-go -s1 -e1 < ../test.txt # 2. \n mode, for normally, startPage oversize and endPage oversize echo "Case 3==================================================" selpg-go -s1 -e2 -l1 ../test.txt echo "Case 4==================================================" selpg-go -s4 -e5 -l1 ../test.txt echo "Case 5==================================================" selpg-go -s1 -e4 -l1 ../test.txt # 3. \f mode, also three test cases echo "Case 6==================================================" selpg-go -s1 -e2 -f ../testf.txt echo "Case 7==================================================" selpg-go -s5 -e6 -f ../testf.txt echo "Case 8==================================================" selpg-go -s1 -e5 -f ../testf.txt # 4. Printer mode, not exist echo "Case 9==================================================" selpg-go -s1 -e2 -l1 -dpl ../test.txt - 运行上述shell文件，得到以下测试结果，经检验结果均正确。
