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c - 当有人使用信号处理输入 "CTRL-C"时,在我的 shell 的历史缓冲区中输出最后 10 个命令

转载 作者:行者123 更新时间:2023-11-30 17:57:14 24 4
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我试图跟踪 shell 中的最后 10 个命令,并让 ctrl + c 信号处理程序输出它们的数组。

显然这个数组只包含10个元素并且总是输出10;这只是暂时的,直到我获得正确的功能为止。

当我在 shell 历史记录中有多个命令时,它会以一种奇怪的顺序多次输出数组,其中某些内容的输出比其他内容多。我猜测这是由子进程也调用处理程序引起的,但我现在不知道该怎么做。 .

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
#include <errno.h>

#define MAX_LINE 80 /* 80 chars per line, per command, should be enough. */
#define BUFFER_SIZE 10

char buffer[BUFFER_SIZE][MAX_LINE];
//char buffer[BUFFER_SIZE];
int pos = 0;
int handleEvent = 0;

void handle_SIGINT()
{
int i = 0;
while (i < BUFFER_SIZE)
{
//printf("%d\n", i);
write(STDOUT_FILENO, buffer[i], strlen(buffer[i]));
printf("\n");
i++;
}
}


void setup(char inputBuffer[], char *args[],int *background)
{
int length, /* # of characters in the command line */
i, /* loop index for accessing inputBuffer array */
start, /* index where beginning of next command parameter is */
ct; /* index of where to place the next parameter into args[] */

ct = 0;

/* read what the user enters on the command line */
length = read(STDIN_FILENO, inputBuffer, MAX_LINE);

start = -1;
if (length == 0)
exit(0); /* ^d was entered, end of user command stream */
if ((length < 0) && (errno !=EINTR)){
perror("error reading the command");
exit(-1); /* terminate with error code of -1 */
}

/* examine every character in the inputBuffer */
for (i = 0; i < length; i++) {
switch (inputBuffer[i]){
case ' ':
case '\t' : /* argument separators */
if(start != -1){
args[ct] = &inputBuffer[start]; /* set up pointer */
ct++;
}
inputBuffer[i] = '\0'; /* add a null char; make a C string */
start = -1;
break;


case '\n': /* should be the final char examined */
if (start != -1){
args[ct] = &inputBuffer[start];
ct++;
}
inputBuffer[i] = '\0';
args[ct] = NULL; /* no more arguments to this command */
break;

case '&':
*background = 1;
inputBuffer[i] = '\0';
break;

default : /* some other character */
if (start == -1)
start = i;
}
}
args[ct] = NULL; /* just in case the input line was > 80 */
}

int main(void)
{
char inputBuffer[MAX_LINE]; /* buffer to hold the command entered */
int background; /* equals 1 if a command is followed by '&' */
char *args[MAX_LINE/2+1];/* command line (of 80) has max of 40 arguments */

/* set up the signal handler */
struct sigaction handler;
handler.sa_handler = handle_SIGINT;
//handler.sa_flags = 0;
//sigemptyset(&handler.sa_mask);
sigaction(SIGINT, &handler, NULL);

while (1){ /* Program terminates normally inside setup */
background = 0;
printf("COMMAND->");
fflush(0);
setup(inputBuffer, args, &background); /* get next command */

strcpy(buffer[pos], inputBuffer);
pos++;

int pid;
int returnValue;

pid = fork(); /* for a child process */

if (pid < 0) { /* check if error occurred with child process */
fprintf(stderr, "Fork Failed");
return 1;
}
else if (pid == 0) { /* child process */
execvp(args[0], args);
}
//else {
if (background == 0){ /* check if the parent should wait */
//wait(&returnValue);
waitpid(pid, NULL, 0);
}
//}

/* the steps are:
(1) fork a child process using fork()
(2) the child process will invoke execvp()
(3) if background == 0, the parent will wait,
otherwise returns to the setup() function. */
}
}

最佳答案

我至少看到两件事:

  • 如果出现错误(例如,如果您尝试运行未知命令),execvp 将返回,因此您需要在 execvp 之后添加 return 语句。
  • read 不会读取字符串 char 的末尾,因此您需要类似 inputBuffer[length] = '\0';

此外,当您按 Ctrl+C 时,我认为您也会从 read() 返回并将 inputBuffer 的最后一个值添加到您的历史记录中。

希望这有帮助。

关于c - 当有人使用信号处理输入 "CTRL-C"时,在我的 shell 的历史缓冲区中输出最后 10 个命令,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/12947182/

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