我正在尝试按名称对文件内容进行排序 这是代码
#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);
}
我将内容放在一个结构中，然后按名称对结构进行排序并将其再次添加到文件中 当我运行它时，文件中没有任何改变
答案 0 :(得分：0)
您是否考虑过使用qsort()功能？
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);
答案 1 :(得分：0)
// 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