从 Bash 管道输入到 C++ cin
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Pipe an input to C++ cin from Bash
提问by Tyler
I'm trying to write a simple Bash script to compile my C++ code, in this case it's a very simple program that just reads input into a vector and then prints the content of the vector.
我正在尝试编写一个简单的 Bash 脚本来编译我的 C++ 代码，在这种情况下，它是一个非常简单的程序，它只是将输入读入向量，然后打印向量的内容。
C++ code:
C++代码：
#include <string>
#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<string> v;
string s;
while (cin >> s)
v.push_back(s);
for (int i = 0; i != v.size(); ++i)
cout << v[i] << endl;
}
Bash script run.sh:
Bash 脚本 run.sh：
#! /bin/bash
g++ main.cpp > output.txt
So that compiles my C++ code and creates a.out and output.txt (which is empty because there is no input). I tried a few variations using "input.txt <" with no luck. I'm not sure how to pipe my input file (just short list of a few random words) to cin of my c++ program.
这样就编译了我的 C++ 代码并创建了 a.out 和 output.txt（它是空的，因为没有输入）。我使用“input.txt <”尝试了一些变体，但没有成功。我不确定如何将我的输入文件（只是一些随机单词的简短列表）通过管道传输到我的 C++ 程序的 cin。
回答by jxh
You have to first compile the program to create an executable. Then, you run the executable. Unlike a scripting language's interpreter, g++does not interpret the source file, but compiles the source to create binary images.
您必须首先编译程序以创建可执行文件。然后，您运行可执行文件。与脚本语言的解释器不同，g++它不解释源文件，而是编译源文件以创建二进制图像。
#! /bin/bash
g++ main.cpp
./a.out < "input.txt" > "output.txt"
回答by luke
g++ main.cppcompiles it, the compiled program is then called 'a.out' (g++'s default output name). But why are you getting the output of the compiler?
I think what you want to do is something like this:
g++ main.cpp编译它，编译后的程序被称为“a.out”（g++ 的默认输出名称）。但是你为什么要得到编译器的输出呢？我认为你想做的是这样的：
#! /bin/bash
# Compile to a.out
g++ main.cpp -o a.out
# Then run the program with input.txt redirected
# to stdin and the stdout redirected to output.txt
./a.out < input.txt > output.txt
Also as Lee Avitalsuggested to properly pipe an input from the file:
同样Lee Avital建议从文件中正确管道输入：
cat input.txt | ./a.out > output.txt
The first just redirects, not technically piping. You may like to read David Oneill's explanation here: https://askubuntu.com/questions/172982/what-is-the-difference-between-redirection-and-pipe
第一个只是重定向，而不是技术上的管道。你可能想在David Oneill这里阅读解释：https: //askubuntu.com/questions/172982/what-is-the-difference-between-redirection-and-pipe
