struct problem undeclared (first use in this function)

I trying to do a program let user input a host name which can't more than 10 characters and follow by input the IP address , the program need to validate the IP that user input is correct . The the end store the information in the struct and print out the host name and IP address once user finish input.(do 5 times)

The program can be compile ,but the program is hang and quit after finish input,doesn't print out any result.

Here is my code

Code:

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#include <stdio.h>#include <stdlib.h>
#include <string.h>
 
#define DELIM "."
#define MAX 10


typedef struct data
{
     
  int a;
  int b;
  int c;
  int d;
  char host[MAX];
}IP;
//IP = {a,b,c,d,"hostname"};


//struct data result[]={};




/* return 1 if string contain only digits, else return 0 */
int valid_digit(char *ip_str)
{
    while (*ip_str) {
        if (*ip_str >= '0' && *ip_str <= '9')
            ++ip_str;
        else
            return 0;
    }
    return 1;
}
/* return 1 if IP string is valid, else return 0 */
int is_valid_ip(char *ip_str)
{
    int i, num, dots = 0;
    char *ptr;
    char *token;
    char *flds[5];
    IP ip;
   
   
    //struct data x;
 
    if (ip_str == NULL)
        return 0;
 
    ptr = strtok(ip_str, DELIM);
   
    //x.a= ptr;
   
    //printf("the %c",result[0].a);
   
   
    if (ptr == NULL)
        return 0;
 
    while (ptr) {
 
        /* after parsing string, it must contain only digits */
        if (!valid_digit(ptr)){
            printf("The ip address should contain digit only\n");
            return 0;
        }
       
        num = atoi(ptr);
       
        //printf("\npart 1 ip: %s\n",ptr);
       
 
        /* check for valid IP */
        if (num >= 0 && num <= 255) {
            /* parse remaining string */
            ptr = strtok(NULL, DELIM);
            //printf("\npart 2 ip: %s",ptr);
            if (ptr != NULL)
                ++dots;
               
        } else{
            printf("The ip address range should be 0~25\n");
            return 0;
        }
           
       
        flds[i] = ptr;   
        i++;
        ptr = strtok(NULL, DELIM);
       
        ip.a = atoi(flds[0]);
        ip.b = atoi(flds[1]);
        ip.c = atoi(flds[2]);
        ip.d = atoi(flds[3]);
        strcpy(ip.host, flds[4]);
       


    }
 
    /* valid IP string must contain 3 dots */
    if (dots != 3){
        printf("invalid format for ip address. should be x.x.x.x\n");
        return 0;   
    }
    return 1;
   
}
 
int main()
{
    int i;
    //IP ip;
    char *token;
    char *flds[5];
    char ip1[MAX];
    char hostname[MAX];
    //char ip1[] = "128.2500.0.1";
 
    //is_valid_ip(ip1)? printf("Valid\n"): printf("Not valid\n");
    //is_valid_ip(ip2)? printf("Valid\n"): printf("Not valid\n");

    for(i=0;i<6;i++){
       
        printf("Please enter host name\n");
        scanf("%s",&hostname);
        while( strlen(hostname) > MAX)
        {       
            printf("invalid please type again\n");
            scanf("%c",&hostname);
        }   
       
        printf("Please enter ip\n");
        scanf("%s",ip1);
        while(!is_valid_ip(ip1))
        {
                printf("invalid , please enter again\n");
                scanf("%s",ip1);
        }
   
        printf("Valid\n");
        printf("Host :%s\n",hostname);
        printf("The %d Ip address you entered:%s\n",i+1,ip1);
       
        //printf("Host :%s\n",hostname);
        //printf("IP = %d.%d.%d.%d\n", a,b,c,d);
    }
       
    system("PAUSE");
    return 0;
}

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As written, you have a global variable called IP, whose type is 'struct data'.

Perhaps you forgot the typedef?

Code:

---

typedef struct data
{
       
  int a;
  int b;
  int c;
  int d;
  char host[MAX];
}IP;

---

Quote:

---

Originally Posted by Salem

As written, you have a global variable called IP, whose type is 'struct data'.

Perhaps you forgot the typedef?

Code:

---

typedef struct data
{
       
  int a;
  int b;
  int c;
  int d;
  char host[MAX];
}IP;

---

---

thx man , but the program still can't work , the program will hangs and exit without any result

How many characters do you need to store say
192.168.100.200

Is it for example more than #define MAX 10 ?

What about say www.google.com, does that fit in 10 chars?

> but the program still can't work , the program will hangs and exit without any result
It's called debugging - good luck.

Seriously, without you posting exactly what input you do provide, we're not going to be sitting around testing your program in the hope that we stumble into the same problem you're seeing.

Time to whip out a debugger and find out what's happening.

I compiled your program and ran it with gdb, and got:

Code:

---

Please enter host name
fefefe
Please enter ip
1.2.3.4

Program received signal SIGBUS, Bus error.
0x00000000004008d9 in is_valid_ip (ip_str=0x7fffffffdfd0 "1") at ../test.c:88
88                flds[i] = ptr;

---

So, what's wrong there?

Code:

---

(gdb) print i
$1 = 32767

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Uh oh! The value of i is way too big for the array. This is because you haven't initialised it to anything. Uninitialised local variables are full of garbage.

This area looks a bit half finished. You don't seem to have a loop to set the other values in flds. You should initalise it to something too - otherwise if your user hasn't put in enough of an ip address the atoi() calls will go and try to read memory at some random address. More crashes, more hangs....
NULL is probably a safe bet here, but check the docs to see what atoi() does with a NULL pointer.

Valgrind is a great tool for detecting this sort of thing, if you're on Linux.

Quote:

---

Originally Posted by Jing Shan

I trying to do a program let user input a host name which can't more than 10 characters and follow by input the IP address , the program need to validate the IP that user input is correct . The the end store the information in the struct and print out the host name and IP address once user finish input.(do 5 times)

The program can be compile ,but the program is hang and quit after finish input,doesn't print out any result.

Here is my code

Code:

---

#include <stdio.h>#include <stdlib.h>
#include <string.h>
 
#define DELIM "."
#define MAX 10


typedef struct data
{
     
  int a;
  int b;
  int c;
  int d;
  char host[MAX];
}IP;
//IP = {a,b,c,d,"hostname"};


//struct data result[]={};




/* return 1 if string contain only digits, else return 0 */
int valid_digit(char *ip_str)
{
    while (*ip_str) {
        if (*ip_str >= '0' && *ip_str <= '9')
            ++ip_str;
        else
            return 0;
    }
    return 1;
}
/* return 1 if IP string is valid, else return 0 */
int is_valid_ip(char *ip_str)
{
    int i, num, dots = 0;
    char *ptr;
    char *token;
    char *flds[5];
    IP ip;
   
   
    //struct data x;
 
    if (ip_str == NULL)
        return 0;
 
    ptr = strtok(ip_str, DELIM);
   
    //x.a= ptr;
   
    //printf("the %c",result[0].a);
   
   
    if (ptr == NULL)
        return 0;
 
    while (ptr) {
 
        /* after parsing string, it must contain only digits */
        if (!valid_digit(ptr)){
            printf("The ip address should contain digit only\n");
            return 0;
        }
       
        num = atoi(ptr);
       
        //printf("\npart 1 ip: %s\n",ptr);
       
 
        /* check for valid IP */
        if (num >= 0 && num <= 255) {
            /* parse remaining string */
            ptr = strtok(NULL, DELIM);
            //printf("\npart 2 ip: %s",ptr);
            if (ptr != NULL)
                ++dots;
               
        } else{
            printf("The ip address range should be 0~25\n");
            return 0;
        }
           
       
        flds[i] = ptr;   
        i++;
        ptr = strtok(NULL, DELIM);
       
        ip.a = atoi(flds[0]);
        ip.b = atoi(flds[1]);
        ip.c = atoi(flds[2]);
        ip.d = atoi(flds[3]);
        strcpy(ip.host, flds[4]);
       


    }
 
    /* valid IP string must contain 3 dots */
    if (dots != 3){
        printf("invalid format for ip address. should be x.x.x.x\n");
        return 0;   
    }
    return 1;
   
}
 
int main()
{
    int i;
    //IP ip;
    char *token;
    char *flds[5];
    char ip1[MAX];
    char hostname[MAX];
    //char ip1[] = "128.2500.0.1";
 
    //is_valid_ip(ip1)? printf("Valid\n"): printf("Not valid\n");
    //is_valid_ip(ip2)? printf("Valid\n"): printf("Not valid\n");

    for(i=0;i<6;i++){
       
        printf("Please enter host name\n");
        scanf("%s",&hostname);
        while( strlen(hostname) > MAX)
        {       
            printf("invalid please type again\n");
            scanf("%c",&hostname);
        }   
       
        printf("Please enter ip\n");
        scanf("%s",ip1);
        while(!is_valid_ip(ip1))
        {
                printf("invalid , please enter again\n");
                scanf("%s",ip1);
        }
   
        printf("Valid\n");
        printf("Host :%s\n",hostname);
        printf("The %d Ip address you entered:%s\n",i+1,ip1);
       
        //printf("Host :%s\n",hostname);
        //printf("IP = %d.%d.%d.%d\n", a,b,c,d);
    }
       
    system("PAUSE");
    return 0;
}

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It seem that you declared the variable of struct "IP" in the function is_valid_ip but you have to and it's best to declare like so

Code:

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typedef struct data
{
       
  int a;
  int b;
  int c;
  int d;
  char host[MAX];
}data;

//declare in main
data ip;

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