C语言实现Shell脚本重定向函数check4redirection（char **arg_array, shellstatus *status）和执行函数execute(char **arg_array, shellstatus status)代码

以下是一个简单的实现，仅支持重定向到文件或管道：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>

typedef struct {
    int redirect_stdout;
    char *output_file;
    int redirect_stdin;
    char *input_file;
    int pipe_to_next;
} redirection_info;

typedef struct {
    int last_status;
} shellstatus;

void parse_redirection(char **arg_array, redirection_info *redir_info) {
    int i;
    for (i = 0; arg_array[i]; i++) {
        // Output redirection
        if (strcmp(arg_array[i], ">") == 0) {
            if (arg_array[i+1]) {
                redir_info->redirect_stdout = 1;
                redir_info->output_file = arg_array[i+1];
                arg_array[i] = NULL; // Remove redirection symbol from arg list
                arg_array[i+1] = NULL; // Remove output file name from arg list
            } else {
                printf("Error: missing output file name after >\n");
            }
        // Input redirection
        } else if (strcmp(arg_array[i], "<") == 0) {
            if (arg_array[i+1]) {
                redir_info->redirect_stdin = 1;
                redir_info->input_file = arg_array[i+1];
                arg_array[i] = NULL; // Remove redirection symbol from arg list
                arg_array[i+1] = NULL; // Remove input file name from arg list
            } else {
                printf("Error: missing input file name after <\n");
            }
        // Pipe to next command
        } else if (strcmp(arg_array[i], "|") == 0) {
            redir_info->pipe_to_next = 1;
            arg_array[i] = NULL; // Remove pipe symbol from arg list
        }
    }
}

void execute(char **arg_array, shellstatus status) {
    pid_t pid;
    int status_code;

    redirection_info redir_info;
    redir_info.redirect_stdout = 0;
    redir_info.output_file = NULL;
    redir_info.redirect_stdin = 0;
    redir_info.input_file = NULL;
    redir_info.pipe_to_next = 0;

    parse_redirection(arg_array, &redir_info);

    pid = fork();
    if (pid == 0) {
        // Child process - execute command
        if (redir_info.redirect_stdout) {
            int fd = open(redir_info.output_file, O_WRONLY|O_CREAT|O_TRUNC, 0666);
            if (fd < 0) {
                printf("Error: cannot open output file %s\n", redir_info.output_file);
                exit(1);
            }
            dup2(fd, STDOUT_FILENO);
            close(fd);
        }
        if (redir_info.redirect_stdin) {
            int fd = open(redir_info.input_file, O_RDONLY);
            if (fd < 0) {
                printf("Error: cannot open input file %s\n", redir_info.input_file);
                exit(1);
            }
            dup2(fd, STDIN_FILENO);
            close(fd);
        }
        if (redir_info.pipe_to_next) {
            int pipefd[2];
            pipe(pipefd);
            pid_t pipe_pid = fork();
            if (pipe_pid == 0) {
                close(pipefd[1]);
                dup2(pipefd[0], STDIN_FILENO);
                close(pipefd[0]);
                execvp(arg_array[0], arg_array);
                printf("Error: cannot execute command %s\n", arg_array[0]);
                exit(1);
            } else if (pipe_pid > 0) {
                close(pipefd[0]);
                dup2(pipefd[1], STDOUT_FILENO);
                close(pipefd[1]);
                execvp(arg_array[0], arg_array);
                printf("Error: cannot execute command %s\n", arg_array[0]);
                exit(1);
            } else {
                printf("Error: cannot fork process\n");
            }
        } else {
            execvp(arg_array[0], arg_array);
            printf("Error: cannot execute command %s\n", arg_array[0]);
            exit(1);
        }
    } else if (pid > 0) {
        // Parent process - wait for child to finish
        waitpid(pid, &status_code, 0);
        status.last_status = WIFEXITED(status_code) ? WEXITSTATUS(status_code) : -1;
    } else {
        printf("Error: cannot fork process\n");
    }
}

int main() {
    char command[1024];
    char *arg_array[256];
    int i;

    shellstatus status;
    status.last_status = 0;

    while (1) {
        printf(">");
        fgets(command, sizeof(command), stdin);
        if (command[strlen(command)-1] == '\n') {
            command[strlen(command)-1] = '\0'; // Remove trailing newline
        }
        if (strlen(command) == 0) {
            continue; // Ignore empty command
        }

        // Split command into args
        char *token = strtok(command, " ");
        i = 0;
        while (token != NULL && i < 256) {
            arg_array[i] = token;
            token = strtok(NULL, " ");
            i++;
        }
        arg_array[i] = NULL;

        execute(arg_array, status);
    }

    return 0;
}