hongzicong/Selpg_GO

Selpg_GO

Selpg_GO is a Go version rewritten a Linux CLI named selpg and the original source code of selpg is written in c.

Introduction

Selgo_GO can be used to extract only a specified range of pages from an input text file and then print the output file in the command line, a file or anywhere you like.

File Structure

• selpg.go: the Go version of selpg

• input_file: the file used to input

• output_file: the file used to output result

• error_file: the file used to output error record

Code Analysis

1. Import required packages in the project.

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"os/exec"

	flag "pflag"
)

2. A struct which is the core of selpg.

type sp_args struct {
	start_page  int
	end_page    int
	in_filename string
	page_len    int
	page_type   bool
	print_dest  string
}

3. Input the arguments of command line, check them for validity and then construct a sp_args struct based on the user's input arguments.

func (sa *sp_args) process_args()

4. Process the input and output the result and error record into the specified locations accroding to the sp_args.

func (sa sp_args) process_input()

Test Case

Typng an instruction $ sh ./test.sh in command line.

// test.sh
for i in {1..7200}
do
  echo $i >> input_file
done

Then we can get a text file consisting of 7200 numbers from 1 to 7200 and each number occupies one line.

Case 1

input: $ selpg -s1 -e1 input_file

output:

// location: command line
1
2
...
72
E:\大三上各科\服务计算\selpg.exe: done

Case 2

input: $ selpg -s1 -e1 < input_file

output:

// location: command line
1
2
...
72
E:\大三上各科\服务计算\selpg.exe: done

Case 3

input: $ selpg -s1 -e1 input_file >output_file

output:

// location: output_file
1
2
...
72

// location: command line
E:\大三上各科\服务计算\selpg.exe: done

Case 4

input: $ selpg -s1 -e1 input_file 2>error_file

output:

// location: command line
1
2
...
72

// location: error_file
E:\大三上各科\服务计算\selpg.exe: done

Case 5

input: $ selpg -s1 -e10 -l1 input_file 2>error_file

output:

// location: command line
1
2
...
10

// location: error_file
E:\大三上各科\服务计算\selpg.exe: done

Reference

1. 开发 Linux 命令行实用程序

2. Golang reference

3. 琦哥正义的帮♂助