selpg-in-Go

An assignment for course : service computing.

Selpg

Selpg represents SELect PaGes.

It allows the user to extract the range of a text specifically. The input text can be from a file or a process.

Development Environment

Ubuntu : 16.04-desktop-amd64
Golang : go1.6.2 linux/amd64
Atom : 1.21.0

Build Setup

go get github.com/renleimlj/selpg-in-Go

Usage

selpg -s=Number -e=Number [options] [filename]

-l ---------- Determine the number of lines per page and default is 72.
-f ---------- Determine the type and the way to be seprated.
-d ---------- Determine the destination of output.
[filename] ---------- Read input from this file.
If filename is not given, it will read input from stdin. Ctrl+D to cutout.

Use package flag

Package flag can be used to analysis the command tag easily.

flag.Usage = func(){} is a function to output the defined command arguments and usage message.
flag.XxxVar() can be used to bound tag to a specified variable.
flag.Parse() can be used to analysis the command arguments and pass them into defined tags eventually.

Use package bufio

Package bufio provides operations to achieve I/O with buffer memory.

func NewScanner(r io.Reader) *Scanner : NewScanner create and return a Scanner which reads data from r and the default cut-apart function is ScanLines.
func NewReader(rd io.Reader) *Reader : NewReader create and return a Reader which reads data from file rd.

Test

Create a txt file named test.txt to test if this selpg code can run and get correct response.

FROM fairest creatures we desire increase,
That thereby beauty's rose might never die,
But as the riper should by time decease,
His tender heir might bear his memory;
But thou, contracted to thine own bright eyes,
Feed'st thy light's flame with self-substantial fuel,
Making a famine where abundance lies,
Thyself thy foe, to thy sweet self too cruel.
Thout that are now the world's fresh ornament
And only herald to the gaudy spring,
Within thine own bud buriest thy content
And, tender churl, mak'st waste in niggarding.
Pity the world, or else this glutton be,
To eat the world's due, by the grave and thee.
WHEN forty winters shall besiege thy brow
And dig deep trenches in thy beauty's field,
Thy youth's proud livery, so gazed on now,
Will be a tottered weed of small worth held:
Then being asked where all thy beauty lies,
Where all the treasure of thy lusty days,
To say within thine own deep-sunken eyes
Were an all-eating shame and thriftless praise.
How much more prasie deserved thy beauty's use
If thou couldst answer, 'This fair child of mine
Shall sum my count and make my old excuse,'
Proving his beauty by succession thine.
This were to be new made when thou art old
And see thy blood warm when thou feel'st cold.

Test selpg -s 1 -e 1 -l 20 test

  To say within thine own deep-sunken eyes
  Were an all-eating shame and thriftless praise.
  How much more prasie deserved thy beauty's use
  If thou couldst answer, 'This fair child of mine
  Shall sum my count and make my old excuse,'
  Proving his beauty by succession thine.
  This were to be new made when thou art old
  And see thy blood warm when thou feel'st cold.

Test cat test | selpg -s 2 -e 3 -l 5

  Within thine own bud buriest thy content
  And, tender churl, mak'st waste in niggarding.
  Pity the world, or else this glutton be, 
  To eat the world's due, by the grave and thee.
  WHEN forty winters shall besiege thy brow
  And dig deep trenches in thy beauty's field,
  Thy youth's proud livery, so gazed on now,
  Will be a tottered weed of small worth held:
  Then being asked where all thy beauty lies,
  Where all the treasure of thy lusty days,

Test selpg -s=1 -e=1 -l 6 < test

  Making a famine where abundance lies,
  Thyself thy foe, to thy sweet self too cruel.
  Thout that are now the world's fresh ornament
  And only herald to the gaudy spring,
  Within thine own bud buriest thy content
  And, tender churl, mak'st waste in niggarding.
  Pity the world, or else this glutton be, 
  To eat the world's due, by the grave and thee.
  WHEN forty winters shall besiege thy brow
  And dig deep trenches in thy beauty's field,
  Thy youth's proud livery, so gazed on now,
  Will be a tottered weed of small worth held:

Test selpg -s 2 -e 2 -l 5 test >output

  Within thine own bud buriest thy content
  And, tender churl, mak'st waste in niggarding.
  Pity the world, or else this glutton be, 
  To eat the world's due, by the grave and thee.
  WHEN forty winters shall besiege thy brow

以上是output文件中的内容，可以通过 more output 来查看。

Test selpg -s -2 -e 1 -l 5 test >output 2 > error

输入 more output，查看得到usage讲解：

  The following is usage of selpg.
          selpg -s=Number -e=Number [options] [filename]
                  -l ---------- Determine the number of lines per page and default is 72.
                  -f ---------- Determine the type and the way to be seprated.
                  [filename] ---------- Read input from this file.
                  If filename is not given, it will read input from stdin. Ctrl+D to cutout.

输入 more error，得到错误日志：

  The range of the page is invalid

Test selpg -s 2 -l 5 test>output 2>error

输入 more output，查看得到usage讲解：

  The following is usage of selpg.
          selpg -s=Number -e=Number [options] [filename]
                  -l ---------- Determine the number of lines per page and default is 72.
                  -f ---------- Determine the type and the way to be seprated.
                  [filename] ---------- Read input from this file.
                  If filename is not given, it will read input from stdin. Ctrl+D to cutout.

输入 more error，得到错误日志：

  selpg: not enough arguments
  selpg: 2nd arg should be -eend_page

Test ./selpg -s 1 -e 2 -l 2 test | go run scanner.go

新建一个scanner.go文件，内容如下：

  package main

  import (
      "fmt"
      "os"
      "bufio"
  )

  func main() {
      scanner := bufio.NewScanner(os.Stdin)
      for scanner.Scan() {
          fmt.Printf("scanner: " + scanner.Text() + "\n")
      }
  }

运行./selpg -s 1 -e 2 -l 2 test | go run scanner.go得到：

  scanner: But as the riper should by time decease,
  scanner: His tender heir might bear his memory;
  scanner: But thou, contracted to thine own bright eyes,
  scanner: Feed'st thy light's flame with self-substantial fuel,

Test ./selpg -s 1 -e 2 -l 2 -d printer test

由于缺乏打印设备来测试结果是否正确，这里我自动将-d命令替换成cat -n来进行测试，结果也正确。

  But as the riper should by time decease,
  His tender heir might bear his memory;
  But thou, contracted to thine own bright eyes,
  Feed'st thy light's flame with self-substantial fuel,