Problem with a feature in a shell program.

Question

This Program works fine with exception for one aspect of smarthistory(). I cannot figure out why when I enter a command number from the smarthistory array why it doesn't execute. After entering the command to execute from the list nothing happens not even the printf statement right after. I am using the gcc compiler.

const int MAX_HISTORY=100;

const int MAX_COMMAND_LENGTH=64;

char history[100][64];
int historyCount = 0;
char smarthistory[100][64];
int smarthistoryCount=0;

void chopnl(char *s) { //strip '\n'
    s[strcspn(s, "\n")] = '\0';
}

void printHistory() {
    int i;
    for (i = 0; i < historyCount; i++)
        printf("%d | %s\n", i, history[i]);
}

void printSmartHistory() {
    int i;
    for (i = 0; i < smarthistoryCount; i++)
        printf("%d | %s\n", i, smarthistory[i]);
}

void isPartialMatch(char *commandQuery,char *history, int historyString)
{
    int lengthOfQuery=strlen(commandQuery);
    if(strncmp( history, commandQuery,lengthOfQuery)==0)
    {
        memcpy(smarthistory[smarthistoryCount++], history, strlen(history) + 1);
    }
    else
        return;

}

void smartHistory()
{
    char commandQuery[MAX_COMMAND_LENGTH];
    int commandNumber=0;
    int i=0;
    printHistory();
    printf("enter partial command:> ");
    fgets(commandQuery,MAX_COMMAND_LENGTH,stdin);
    chopnl(commandQuery);
    //printf("%d", strlen(commandQuery));

    for(i=0;i<=historyCount;i++)
    {
            isPartialMatch(commandQuery, history[i], i);
    }
    printf("SmartHistory Search Results\n");
    printSmartHistory();
    printf("enter a command number to execute:> ");
    scanf("%d", commandNumber);
    //chopnl(commandNumber);
    printf("command entered >");
    handleCommand(smarthistory[commandNumber]);
}
void placeInHistory(char *command) {
    // printf("command:> %s |stored in:> %d",command,historyCount );
    memcpy(history[historyCount++], command, strlen(command) + 1);
}

int main(int argc, char** argv) {
    char command[MAX_COMMAND_LENGTH];

    while (1) {
        printf("SHELL:>");
        fgets(command, MAX_COMMAND_LENGTH, stdin);
        chopnl(command);
        if (strcmpi(command, "exit") == 0)
            return EXIT_SUCCESS;
        placeInHistory(command);
        handleCommand(command);
    }
    return (EXIT_SUCCESS);
}

int handleCommand(char *command) {
    pid_t pid;
    int test=0;
    pid = fork();

    if (pid > 0) {
        wait(&test);
    } else if (pid == 0) {
        execCommand(command);
        exit(0);
    } else {
        printf("ERROR");
    }
}

int execCommand(char *command) {
    //system(command);    

    if (strcmpi(command, "history") == 0)
    {
        printHistory();
    }
    else if(strcmpi(command, "smarthistory") == 0)
    {
        smartHistory();
    }
    else if (strcmpi(command, "ls") == 0 || (strcmpi(command, "pwd") == 0)) {
        char *path[] = {"/bin/", NULL};
        strcat(path[0], command);
        execve(path[0], path, NULL);
    }else{system(command);}
}

Answer 1

Recheck this:

char *path[] = {"/bin/", NULL};
strcat(path[0], command);

path[0] is initialised with const char*, and you cannot use strcat() on that.

Another one:

memcpy(smarthistory[smarthistoryCount++], history, strlen(history) + 1);

shouldn't both, source and destination, be of the same type, char*?

Also, I'd suggest to use char* history[MAX_HLEN]

instead of char history[x][y].

Answer 2

I'm not sure, but it looks like the handling of "history" and "smarthistory" should be moved from execCommand to handleCommand and should occur INSTEAD OF forking. There may be other bugs.

Answer 3

Problem solved the problem was I needed to add an '&' before commandNumber in the statement: scanf("%d", commandNumber); located in the smartHistory function. What strikes me as odd is I made another version of this where I moved the "history" and "smarthistory" into the handle command function instead of the execCommand function. When I did this the program prints the shell prompt 3 times...if anyone knows why, please let me know. However in the version above just adding the '&' works great.