сортировочного содержимое файла

Question

я пытаюсь сортировать содержимое файла по имени здесь код

#include <iostream> 
#include<string.h> 

/* run this program using the console pauser or add your own getch, system("pause") or input loop */ 
struct Contacts 
{ 
    char name[20]; 
    int phone; 
    char address[20]; 

}; 


int countLines(FILE * fp); 
void sort_contact(int length , FILE * f); 
int main(int argc, char** argv) { 
    FILE *f=fopen("D:\\eman.txt","r"); 
    int c; 
    c=countLines(f); 

    printf("number of lines %d",c); 


    sort_contact(c , f); 
    return 0; 
} 


int countLines(FILE * fp){ 
    char line[80]; 
    int counter = 0; 
    while (fgets(line, sizeof line, fp)){ 


     counter+=1; 

    } 
    return counter; 
} 



void sort_contact(int length , FILE * f) 
    { 
    // struct Contacts * eman [length]; 
     int flag; 
     int i; // for loop counter 
     struct Contacts con; 
     struct Contacts tmp; 
     struct Contacts conn; 
     struct Contacts users[length]; 
     //f=fopen("","r";) 
     //while((fscanf(f, "%s %d %s ", con.name ,&con.phone,con.address) != EOF) && (length > 0) ) 

     while((fscanf(f, "%s %d %s ", users[length].name ,&users[length].phone,users[length].address) != EOF) && (length > 0) ) 
      { 
       con=users[length]; 
      conn=users[length--]; 
       flag=strcmp(con.name,conn.name); 
       //length --; 


      switch(flag) 
      { 
       case 1: 
        tmp=users[length--]; 
        users[length--]=users[length]; 
        users[length]=tmp; 
        break; 

       case 0: 
       case -1: 
       break; 

      } 

     length --; 
     //seek(fd, 0, SEEK_END); 
    }//end fo while 
      fclose(f); 
      f=fopen("D:\\eman.txt","+w"); 
      for(i=length;i>0;i--) 
      { 
      // tmp=users[i]; 
       fprintf(f,"%s %d %s",users[i].name,users[i].phone, users[i].address); 
      } 
      fclose(f); 



} 

я поместить содержимое в структуре, а затем отсортировать структуру по имени и добавить его снова файл , когда я его запускаю, ничего не изменяется в файле

Answer 1

Вы считаете, что используете функцию qsort()?

int compare_contact (const void * a, const void * b) 
{ 
    Contacts* left = (Contacts*) a; 
    Contacts* right = (Contacts*) b; 
    return strncmp(left.name,right.name, sizeof Contacts.name); 
} 

qsort(pUsers, length, sizeof Contacts, compare_contact);

Answer 2

// the following is a clean compile of your program 
// with the algorithm logic corrected (and several other details) 
// with checking of returned values from output I/O statements 
// with checking of returned value from malloc and calloc 
// with modification to the input and output format strings 
// Note: 
// 1) if the sizing of name and address fields is inadequate 
//  for actual values in input file 
//  then this algorithm will fail 
// 2) if any line in the input file is longer than 80 chars 
//  then this algorithm will fail 
// 3) when reading a line from the file into pUsers[] 
//  it would be far safer (and can validate format of line contents) 
//  to read the line into a temporary area like: char line[80] 
//  then parse the fields using something like: sscanf() 
//  then malformed lines can be recognized/discarded 
// suggest breaking the sort_contact() function into three functions: 
// 1) read the input file into pUsers[] 
// 2) sort pUsers[] 
// 3) write the new file 


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

/* run this program using the console pauser or add your own getch, system("pause") or input loop */ 
struct Contacts 
{ 
    char name[20]; // what if name is longer than 19 char in file 
    int phone; 
    char address[20]; // what if address is longer than 19 char in file 
}; 

// prototypes 
int countLines(FILE *); 
void sort_contact(int, FILE *); 

// place outside of any function because it could be HUGE, 
// depending on input file size 
// and do not want to put all that on the stack 
static struct Contacts* pUsers = NULL; 

int main() 
{ 
    int lineCount = 0; 
    FILE *inf=fopen("D:\\eman.txt","r"); 
    if (NULL == inf) 
    { 
     perror("fopen failed for read of eman.txt"); 
     exit(EXIT_FAILURE); 
    } 

    // implied else, fopen successful 

    lineCount = countLines(inf); 

    if(0 < lineCount) 
    { 
     printf("number of lines in input file: %d", lineCount); 

     // note: using calloc removes need to terminate each string later 
     if(NULL == (pUsers = calloc(lineCount, sizeof(struct Contacts)))) 
     { // then calloc failed 
      perror("calloc failed for input array"); 
      fclose(inf); 
      exit(EXIT_FAILURE); 
     } 

     // implied else, malloc successful 

     sort_contact(lineCount, inf); 

     free(pUsers); // cleanup 
    } 

    else 
    { 
     printf("no lines read from input file\n"); 
    } 

    fclose(inf); // cleanup 

    return 0; 
} // end function: main 


int countLines(FILE * inf) 
{ 
    char line[80]; // what if some line is greater than 79 characters or contains nulls? 
    int counter = 0; 
    while (fgets(line, sizeof line, inf)) 
    { 
     counter+=1; 
    } // end while 

    rewind(inf); // cleanup 

    return counter; 
} // end function: countLines 


void sort_contact(int lineCount, FILE * inf) 
{ 
    int i = 0;   // write loop counter 
    int currentLine = 0; // read loop counter 
    int retFscanf=0;  // returned value from fscanf 

    int c; // outer sort loop counter 
    int d; // inner sort loop counter 

    struct Contacts tmp; 

    // read all lines from file into pUsers array 
    for(currentLine=0; currentLine < lineCount; currentLine++) 
    { 
     retFscanf = fscanf(inf, " %19s %d %19s", // note leading space in format string, no trailing space 
       pUsers[currentLine].name , 
       &pUsers[currentLine].phone, 
       pUsers[currentLine].address); 
     if(3 != retFscanf) 
     { // then, fscanf failed 
      perror("fscanf failed"); 
      fclose(inf); // cleanup 
      free(pUsers); // cleanup 
      exit(EXIT_FAILURE); 
     } 

     // implied else, fscanf successful 
    } // end for 

    // implement bubble sort here 

    for (c = 0 ; c < (lineCount-1); c++) 
    { // whole array 

     for (d = 0 ; d < (lineCount - c - 1); d++) 
     { // current subset of whole array 

      if (0 < (strcmp(pUsers[d].name, pUsers[d+1].name ))) 
      { // then, earlier name sorts after next name 
       memcpy(&tmp,   &pUsers[d], sizeof(struct Contacts)); 
       memcpy(&pUsers[d], &pUsers[d+1], sizeof(struct Contacts)); 
       memcpy(&pUsers[d+1], &tmp,   sizeof(struct Contacts)); 
      } // end if 
     } // end for 
    } // end for 

    FILE * outf; 
    if(NULL == (outf = fopen("D:\\eman.txt","+w"))) 
    { // then fopen failed 
     perror("fopen failed for write"); 
     free(pUsers); // cleanup 
     fclose(inf); // cleanup 
     exit(EXIT_FAILURE); 
    } // endif 

    // implied else fopen successful 

    for(i=0;i<lineCount;i++) 
    { 
      fprintf(outf,"%s %d %s\n",pUsers[i].name, pUsers[i].phone, pUsers[i].address); 
    } // end for 

    fclose(outf); // cleanup 
} // end function: sort_contact