如何在shell脚本中处理ctrl+c？

Question

我正在尝试在 shell 脚本中处理 ctrl+c 。我的代码在 while 循环中运行，但我从 shell 脚本调用二进制文件并在后台运行它，因此当我想停止二进制文件时，它应该停止。代码如下hello.c

#include <stdio.h>
    
int main()
{
    while(1)
    {
        int n1,n2;
        printf("Enter the first number\n");
        scanf("%d",&n1);
        printf("Enter the second number\n");
        scanf("%d",&n2);
        printf("Entered number are n1 = %d , n2 =%d\n",n1,n2);
    }
}

下面是我使用的 bash 脚本。

#/i/bin/sh
echo run the hello binary
./hello < in.txt &

trap_ctrlc()
{
    ps -eaf | grep hello | grep -v grep | awk  '{print $2}' | xargs kill -9
    echo trap_ctrlc
    exit
}

trap trap_ctrlc SIGHUP SIGINT SIGTERM

启动脚本后，hello 二进制文件将持续运行。我已经使用kill -9 pid 命令从其他终端杀死了这个二进制文件。

我尝试过 trap_ctrlc 函数，但它不起作用。如何在shell脚本中处理ctrl+c？

我已经in.txt添加了输入，因此我可以将此文件直接传递给二进制文件。

1
2

输出：

Enter the first number  
Enter the second number  
Entered number are n1 = 1 , n2 =2  
Enter the first number    
Enter the second number  
Entered number are n1 = 1 , n2 =2   
Enter the first number    
Enter the second number    
Entered number are n1 = 1 , n2 =2  

而且它持续不断。

Answer 1

更改您的c程序，以便检查读取数据是否确实成功：

#include <stdio.h>

int main()
{
    int n1,n2;
    while(1) {
        printf("Enter the first number\n");
        if(scanf("%d",&n1) != 1) return 0;   /* check here */
        printf("Enter the second number\n");
        if(scanf("%d",&n2) != 1) return 0;   /* check here */
        printf("Entered number are n1 = %d , n2 =%d\n",n1,n2);
    }
}

当输入in.txt耗尽时，它现在将终止。

要制作可多次读取的内容，您可以在bash脚本中创建一个永远循环（或直到被终止）的in.txt循环。./hello

例子：

#!/bin/bash

# a function to repeatedly print the content in "in.txt"
function print_forever() {
    while [ 1 ];
    do
        cat "$1"
        sleep 1
    done
}

echo run the hello binary
print_forever in.txt | ./hello &
pid=$!
echo "background process $pid started"

trap_ctrlc() {
    kill $pid
    echo -e "\nkill=$? (0 = success)\n"
    wait $pid
    echo "wait=$? (the exit status from the background process)"
    echo -e "\n\ntrap_ctrlc\n\n"
}

trap trap_ctrlc INT

# wait for all background processes to terminate
wait

可能的输出：

$ ./hello.sh
run the hello binary
background process 262717 started
Enter the first number
Enter the second number
Entered number are n1 = 1 , n2 =2
Enter the first number
Enter the second number
Entered number are n1 = 1 , n2 =2
Enter the first number
^C
kill=0 (0 = success)

wait=143 (the exit status from the background process)


trap_ctrlc

另一种选择是在wait中断后杀死孩子：

#!/bin/bash

function print_forever() {
    while [ 1 ];
    do
        cat "$1"
        sleep 1
    done
}
 
echo run the hello binary
print_forever in.txt | ./hello &
pid=$!
echo "background process $pid started"
 
trap_ctrlc() {
    echo -e "\n\ntrap_ctrlc\n\n"
}
 
trap trap_ctrlc INT
 
# wait for all background processes to terminate
wait
echo first wait=$?
kill $pid
echo -e "\nkill=$? (0 = success)\n"
wait $pid
echo "wait=$? (the exit status from the background process)"`
``