无法找到无限循环的来源

Question

#include<stdio.h>
#include<stdlib.h>
#include<errno.h>
#include<sys/utsname.h>
#include<string.h>
#include<unistd.h>
#include<sys/types.h>
#include<pwd.h>
#include<sys/wait.h>
#include<signal.h>

#define MAX_NO_OF_CMD_ELEMENTS (10)

struct utsname u; /* to get hostname*/
struct passwd *pw; /*to get username*/
int pid;
char* username, *hostname;
char cwd[100];
char *basedir;
int bg;

void init_prompt()
{
    getcwd(cwd,100);
    basedir = cwd;
    uname(&u);
    pw = getpwuid(getuid());
    username = pw->pw_name;
    hostname = u.nodename;
}


void prompt_me()
{
    sleep(1);
    getcwd(cwd,100);
    bg =0;
    printf("%s@%s:%s$ ",username,hostname,cwd);
}

void pinfo(char **argv)
{
    char path[1024];
    char c;
    char buf[1024];
    char filename[1000];
    printf("pid --- %s\n",argv[1]);
    sprintf(filename,"/proc/%s/status",argv[1]);
    FILE *f = fopen(filename, "r");
    FILE *fp;

    char state;
    fgets(buf,1024,f);
    fgets(buf,1024,f);
    sscanf(buf, "State: %c\n", &state);
    printf("process state = %c\n", state);
    fclose(f);
    char target_path[1024];
    sprintf(filename, "/proc/%d/exe",pid);
    int len = readlink (filename, target_path, sizeof (target_path));
    char buffer[1024];
    if(len ==-1)
    {
        perror("readlink");
    }
    else
    {
        target_path[len] = '\0';
        printf("executable path: %s\n", target_path);
    }
}

void pwd_me()
{
    getcwd(cwd,100);
    printf("%s",cwd); 
}

void cd_me(char **argv)
{
    chdir(argv[1]);
    if(getcwd(cwd,100)!=0)
    {
        perror(" ");
    }
    if(strcmp("~\0",argv[1])==0||strcmp("\0",argv[1])==0)
        chdir(basedir);
}

void echo_me(char **argv,int num)
{
    int i;
    for(i=0;i<num;i++)
    {
        printf("%s", argv[i]);
        if(i!=0 || i!=num-1)
        {
            printf(" ");
        }
    }
}

void execute(char **argv,int num)
{
    int i;
    pid_t  pid;
    int    status;

    if ((pid = fork()) < 0) 
    {     /* fork a child process*/
        printf("*** ERROR: forking child process failed\n");
        exit(1);
    }
    else if (pid == 0) 
    {          /* for the child process: */
        if(strcmp(argv[0],"cd")==0)
            cd_me(argv);
        else if(strcmp(argv[0],"pwd")==0)
            pwd_me();
        else if(strcmp(argv[0],"echo")==0)
            echo_me(argv,num);
        else if(strcmp(argv[0],"pinfo")==0)
            pinfo(argv);
        else if(strcmp(argv[0],"exit")==0)
            return;
        int c;
        if (c==execvp(argv[0], argv) < 0) 
        {     /* execute the command  */
            printf("%d\n", c);
            printf("*** ERROR: exec failed\n");
            perror(" ");
            exit(1);
        }
    }
    else if(bg!=1){
        while (wait(&status) != pid);

    }
}

void input()
{
    int i,j,n,len,c;
    char *buffer = 0;
    size_t bufsize = 0;
    ssize_t characters;
    char *cmd[MAX_NO_OF_CMD_ELEMENTS+1];

    characters = getline(&buffer, &bufsize, stdin);

    len = strlen(buffer);
    buffer[len-1]='\0';

    if (characters > 0)
    {
        char *end_str1;
        char *token1 = strtok_r(buffer, ";", &end_str1);
        int count = 0, wordcnt;
        while (token1 != NULL)
        {
            char *token2;
            memset(cmd,0,sizeof(cmd));
            char * cmd[MAX_NO_OF_CMD_ELEMENTS + 1]; /* 1+ for the NULL-terminator */
            size_t wordcnt = 0;
            char *end_str2;
            count++;
            token2 = strtok_r(token1, " ", &end_str2);
            while ((NULL != token2)
                    && (MAX_NO_OF_CMD_ELEMENTS > wordcnt)) /* Prevent writing
                                                              out of `cmd`'s bounds. */
            {
                cmd[wordcnt] = token2;
                wordcnt++;
                token2 = strtok_r(NULL, " ", &end_str2);
            }
            if(token2==NULL)
            {
                cmd[wordcnt] = NULL;

                execute(cmd, wordcnt);
            }
        }
    }
    free(buffer);
}


int main()
{
    init_prompt();
    while(1)
    {
        prompt_me();
        input();
    }
}

我无法找到运行此程序时发生的无限循环的来源。请帮帮忙？

我认为它最有可能出现在输入功能中，但我不确定是否安全，我将整个程序包括在内。

Answer 1

将以下行添加到while (token1 != NULL)函数中input循环的末尾：

token1 = strtok_r(NULL, ";", &end_str1);

问题是你没有更新token1，因此，token1将永远不会为NULL，因此while (token != NULL)将永远循环。

请参阅The linux man page on strtok_r(3)