C++/Php/Python/Shell 程序按行读取文件或者控制台的实现

#include<stdio.h>
#include<string.h>

int main(){
  const char* in_file = "input_file_name";
  const char* out_file = "output_file_name";

  FILE *p_in = fopen(in_file, "r");
  if(!p_in){
    printf("open file %s failed!!!", in_file);
    return -1;
  }
    
  FILE *p_out = fopen(out_file, "w");
  if(!p_in){
    printf("open file %s failed!!!", out_file);
    if(!p_in){
      fclose(p_in);
    }
    return -1;
  }

  char buf[2048];
  //按行读取文件内容
  while(fgets(buf, sizeof(buf), p_in) != NULL) {
    //写入到文件
    fwrite(buf, sizeof(char), strlen(buf), p_out);
  }

  fclose(p_in);
  fclose(p_out);
  return 0;
}

#include<stdio.h>

int main(){
  char buf[2048];

  gets(buf);
  printf("%s\n", buf);

  return 0;
}

/// scanf 遇到空格等字符会结束
/// gets 遇到换行符结束

<?php
$filename = "input_file_name";

$fp = fopen($filename, "r");
if(!$fp){
  echo "open file $filename failed\n";
  exit(1);
}
else{
  while(!feof($fp)){
    //fgets(file,length) 不指定长度默认为1024字节
    $buf = fgets($fp);

    $buf = trim($buf);
    if(empty($buf)){
      continue;
    }
    else{
      echo $buf."\n";
    }
  }
  fclose($fp);
}
?>

<?php
$fp = fopen("/dev/stdin", "r");

while($input = fgets($fp, 10000)){
    $input = trim($input);
    echo $input."\n";
}

fclose($fp);
?>

#coding=utf-8

# 如果要在python2的py文件里面写中文，则必须要添加一行声明文件编码的注释，否则python2会默认使用ASCII编码。
# 编码申明，写在第一行就好 
import sys

input = sys.stdin

for i in input:
  #i表示当前的输入行

  i = i.strip()
  print i

input.close()

#!/bin/bash

#读取文件, 则直接使用文件名; 读取控制台, 则使用/dev/stdin

while read line
do
  echo ${line}
done < filename

#!/bin/bash

while read line
do
  echo ${line}
done < /dev/stdin