Dtyjlui

Example lines from input file:

abc@gmail.com Andee SMITH 1234

ADAM abc@gmail.com Andeee 21654

Anderea abc@gmail.com SAMMY 3524654

abc@gmail.com Andi BROWN 1245

Andie abc@gmail.com KNOWY 2485

Andra abc@gmail.com BRUCE 52445

Andrea abc@gmail.com 246574 DENNIS

2154 Andreana abc@gmail.com CHASE

Andree 21524 SIERRRA abc@gmail.com

Andrei 154 MONDY abc@gmail.com

4564765 Andria MALLE abc@gmail.com

78 Andriana abc@gmail.com WALLS

579874 abc@gmail.com Andriette MOUNT

52445 abc@gmail.com Andromache FRASSER

5478645 abc@gmail.com Andy MCFLY

//This program about scanning names,surnames ext. from disordered txt file and creating new ordered txt file.



#include<stdio.h>

#include<stdlib.h>

#include<string.h>



typedef struct{



char  id[50];

char name[50];

char lname[50];

char mail[50];



}Person;



int main(){



    char str[250];

    int count=0;

    char c;

    char previous;

    int index =0;

    int i,m,l;

    int j,k=0;

    Person person[300];

    char str1[250];

    char in[1];

    char p;

    Person temp;





    FILE *file= fopen("hw4_disordered_people.txt","r");





    while(c!=EOF){  // how many of struct



        c= fgetc(file);



        if(c=='n'){



        ++count;

        }

    }

    fclose(file);



    //person *person= (person*)malloc(count+1*sizeof(person));



    file = fopen( "hw4_disordered_people.txt" , "r");

    while(fgets(str1,sizeof(str1),file)){

        ++index;

        for (j = 0; str1[j] != 'n'; ++j)

        {

            if (str1[j] != ' ' && str1[j+1] != 'n')

            {

                str[k] = str1[j];

                k++;

            }

            else  if (k > 0 )

            {

                if (str1[j+1] == 'n')

                {

                    str[k] = str1[j];

                    k++;

                }

                str[k] = '';

                k=0;









                if(str[0] >= '0' && str[0] <='9')

                {

                    strcpy(person[index].id,str);

                    //printf("%s ",person[index].id);

                    strcpy(str,"");



                }

                else if (str[1] >= 'A' && str[1] <='Z')

                {



                    if(strlen(person[index].lname) > 0){

                        //printf(" %s ",str);

                        strcat(person[index].lname," ");

                        strcat(person[index].lname,str);

                        strcpy(str,"");

                    }

                    else{

                        strcpy(person[index].lname,str);

                        //printf("%s ",person[index].lname);

                        strcpy(str,"");



                    }



                }

                else if ((str[1] >= 'a' && str[1] <='z') && (str[0] >= 'A' && str[0] <='Z'))

                {



                    if(strlen(person[index].name) > 0){

                        //printf(" %s ",str);

                        strcat(person[index].name," ");

                        strcat(person[index].name,str);

                        strcpy(str,"");

                    }

                    else{

                        strcpy(person[index].name,str);

                        //printf("%s  ",person[index].name);

                        strcpy(str,"");

                    }



                }

                else

                {

                    strcpy(person[index].mail,str);

                    //printf("%s ",person[index].mail);

                    strcpy(str,"");

                }



            }



        }

    }

     FILE *fp;



          fp=fopen("OrderedList.txt","w");

          for(i=1;i<=count;++i){





          fprintf(fp,"%s %s %s %sn",person[i].name,person[i].lname,person[i].mail,person[i].id);

         }

}

Your program has many errors in it, here are a few:

FILE *file= fopen("hw4_disordered_people.txt","r");





while(c!=EOF){  // how many of struct

Here you don't check if opening the file succeeded and you begin to make use of the uninitialized variable c, which can technically have any value sitting in memory assigned to it. Even with the assumed value of 0 this is also still wrong since this assumes that a file is at least 1 byte large meaning this program may do strange things with an empty file passed to it.

while(c!=EOF){  // how many of struct

    c = fgetc(file);



    if(c=='n'){

      ++count;

    }

}

The correct way to write this would be closer to:

while ((c = fgetc(file)) != EOF) {

  ++count;

}

It's also worth noting that this portion of the program can be replaced by using the wc -l command, which counts how many lines exist in a file.

if (str1[j+1] == 'n')

There is no guarantee that j+1 is a valid index into this array.

char str[250];

There is no guarantee that a line in the file won't be 248 characters or longer (including the newline and null terminator)

Person person[300];

There is no guarantee that the input file will be 300 or less lines.

str[k] = '';

k may now point outside the bounds of the character array, although the input needed to do it is a pretty specific edge case.

strcpy(person[index].id,str);

Buffer overflow if index is out of range (300)

for(i=1;i<=count;++i){

This likely attempts to access data outside the bounds of the array. The fact you increment early in the loop and discard index 0 of the array is strange, but not technically an error, but the fact that you are willing to access count + 1 as a valid address is an error and if you were using malloc without a fixed array size or processing a file with 300 inputs this would segmentation fault / crash the program.

You should compile your code with gcc -Wall and you will likely get a lot of these warnings automatically.

If your course material allows it you should be using C++ with the Standard Template Library (STL) in which case this entire program would be a few lines of code that have strong guarantees that it won't have many of the memory errors presented here since it would use std::string and std::istream to make this less of an issue along with std::unordered_map to make lookups faster.