A database that uses a random access file written in C

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<time.h>
#include<stdbool.h>
struct contactinfo{
char name[40];
char number[40];
char email[40];
};

struct filedetails{
int filelength;
int recnum;
};
struct filedetails filespec;
struct contactinfo person;
struct contactinfo blankfields;
FILE *details;
int flag = 0;
char contact[40];
long int offset=0, length;
long int size;
char filename[30];
bool recordfound;
void newsubs(void), search(void), readLine(char buffer[]), new(void), sort(void);
void list(void), delete(void), prntxt(void);
int main(void)
{
int choice;
char ch[3];
for(;;){
printf("\n");
printf("1. New file\n");
printf("2. New record\n");
printf("3. Sort\n");
printf("4. List\n");
printf("5. Search\n");
printf("6. Delete\n");
printf("7. Export to a txt file for printing.\n");
printf("8. Quit:\n");
do{
printf("\nChoose...");
readLine(ch);
choice = atoi(ch);
if(choice==1)new();
if(choice==2)newsubs();
if(choice==3)sort();
if(choice==4)list();
if(choice==5)search();
if(choice==6)delete();
if(choice==7) prntxt();
if(choice==8) exit(0);
}while(choice < 1 && choice > 8);
}
return 0;
}
void readLine(char buffer[])
{
char character;
int i=0;
do
{
character=getchar();
buffer[i]=character;
++i;
}
while(character !='\n');
buffer[i-1]='\0';
}

void newsubs()
{
printf("Enter a file name.\n");
readLine(filename);
printf("\n");
if((details=fopen(filename, "r+b"))==NULL)
{
printf("Cannot open file.\n");
}
if((details=fopen(filename, "r+b"))!=NULL) {

fread(&filespec , sizeof(struct filedetails), 1,details);
printf("Records in file =%d\n",filespec.recnum);
printf("Size of file in bytes = %d\n",filespec.filelength);
printf("Enter information on new contact.\n");
printf("Name:\n");
readLine(person.name);
printf("Phone number:\n");
readLine(person.number);
printf("Email:\n");
readLine(person.email);
size = sizeof(struct contactinfo);
offset=(filespec.recnum +1)*size;
if(fseek(details, offset,0))
printf("Seek error.\n");
length = ftell(details);
printf("Pointer before writing at %ld\n",length);
if(fwrite(&person, sizeof(struct contactinfo), 1,details)==0) {
printf("Write error.");
}
else
{
length = ftell(details);
printf("Pointer after writing at %ld\n",length);
filespec.filelength= length;
filespec.recnum+=1;
rewind(details);
fwrite(&filespec, sizeof(struct filedetails), 1,details);
person = blankfields;
fclose(details);
}
}
}

void search()
{
int searchcount=0;
printf("Enter a file name.\n");
readLine(filename);
printf("\n");
if((details=fopen(filename, "r+b"))==NULL) {
printf("Cannot open file.\n");
}
else
{
if((details=fopen(filename, "r+b"))!=NULL)
flag = 0;
recordfound=0;
fread(&filespec , sizeof(struct filedetails), 1,details);
printf("Enter a name to look for.\n");

readLine(contact);
offset=0;
while(!feof(details))
{
searchcount+=1;
size = sizeof(struct contactinfo);
offset+=size;
if(fseek(details, offset,0)){
printf("Seek error.");
}
else
{
fread(&person, sizeof(struct contactinfo), 1, details);

if(strcmp(contact, person.name)==0)
{
recordfound=1;
printf("%s\n",person.name);
printf("%s\n",person.number);
printf("%s\n",person.email);
printf("\n");
}
if(searchcount == filespec.recnum)break;
}
}
fclose(details);
if(recordfound == 0)
{
printf("Record not found.\n");
}
else
{
if(recordfound == 1) recordfound== 0;
flag = 1;
}
}
}


void new()
{
printf("Enter a file name.\n");
readLine(filename);
printf("\n");
if((details=fopen(filename, "w+b"))==NULL) {
printf("Cannot open file.\n");
}
filespec.recnum=0;
fwrite(&filespec , sizeof(struct filedetails), 1,details);
printf("New file created\n");
fclose(details);
}


void sort()
{
int recnum;
int i;
struct contactinfo temp;
long int u;
long int v;
printf("Enter a file name.\n");
readLine(filename);
printf("\n");
if((details=fopen(filename, "r+b"))==NULL) {
printf("Cannot open file.\n");
}
else
{
fread(&filespec , sizeof(struct filedetails), 1,details);
for(u=1; u<filespec.recnum; u++)
{
for (v=u+1; v<=filespec.recnum; v++){
size = sizeof(person);
fseek(details, sizeof(person)*u,0);
fread(&person, sizeof(person), 1, details);
fseek(details, sizeof(person)*(v),0);
fread(&temp, sizeof(person), 1, details);
if(strcmp(person.name,temp.name)>0)
{
fseek(details, sizeof(person)*(u),0);
fwrite(&temp, sizeof temp, 1,details);
fseek(details, sizeof(person)*(v),0);
fwrite(&person, sizeof(person), 1,details);
}
}
}
fclose(details);
}
}

void list()
{
int counter = 0;
printf("Enter a file name.\n");
readLine(filename);
printf("\n");
if((details=fopen(filename, "r+b"))==NULL) {
printf("Cannot open file.\n");
}
if((details=fopen(filename, "r+b"))!=NULL) {
fread(&filespec , sizeof(struct filedetails), 1,details);
printf("Records in file =%d\n",filespec.recnum);
printf("Size of file in bytes =%d\n", filespec.filelength);
size = sizeof(struct contactinfo);
offset=0;
while(!feof(details))
{
counter +=1;
offset+=size;
if(fseek(details, offset,0)){
printf("Seek error.");
}
else
{
fread(&person, sizeof(struct contactinfo), 1, details);
printf("\n");
printf("%s\n",person.name);
printf("%s\n",person.number);
printf("%s\n",person.email);
printf("\n");
if(counter == filespec.recnum)break;
}
}
fclose(details);
}
}   
   
void delete()
{   

long int offset2=0;
int recordcount;
int counter=0;
int counter2=0;
char filename2[30];
char reply;
FILE *tempfile;
search();
if(flag == 0)
{
printf("Exiting function delete.\n");
}
else
{
if((details=fopen(filename, "r+b"))==NULL)
{
printf("Cannot open file.\n");
}
else
{
if((details=fopen(filename, "r+b"))!=NULL) {
fread(&filespec , sizeof(struct filedetails), 1,details);
recordcount = filespec.recnum;
printf("Enter a file name for the destination of the edited files.\n");
readLine(filename2);
if((tempfile=fopen(filename2, "w+b"))==NULL)
{
printf("Cannot open file.\n");
}
else
{
filespec.recnum=0;
fwrite(&filespec , sizeof(struct filedetails), 1,tempfile);
printf("New file created\n");
fclose(tempfile);
if((tempfile=fopen(filename2, "r+b"))!=NULL)
{
printf("File %s is open for input.\n",filename2);
}
size = sizeof(struct contactinfo);
offset=0;
while(!feof(details))
{
person = blankfields;
counter +=1;
offset+=size;
if(fseek(details, offset,0)){
printf("Seek error.");
}
else
{
fread(&person, sizeof(struct contactinfo), 1, details);
printf("%s\n",person.name);
if(strcmp(contact, person.name)!=0)
{
counter2+=1;
if(counter2 == recordcount) break;
offset2=(counter2)*size;
if(fseek(tempfile, offset2,0)){
printf("Seek error.");
}
else
{
if(fwrite(&person, sizeof(struct contactinfo), 1, tempfile));
length = ftell(tempfile);
}
}
}
}
fclose(details);
filespec.recnum=counter2-1;


filespec.filelength=length;
rewind(tempfile);
fwrite(&filespec , sizeof(struct filedetails), 1,tempfile);
fclose(tempfile);
}
}
}
}
}

void prntxt()
{
int count;
FILE *stream;
char filenametxt[30];
count = 0;
printf("Enter a 'filename.txt' file name to create and write to.\n");
readLine(filenametxt);
printf("\n");
stream = fopen(filenametxt, "w+");
if((details=fopen(filenametxt, "w+"))==NULL) {
printf("Cannot open file.\n");
}
else
{
int counter = 0;
printf("Enter a file name to read records from.\n");
readLine(filename);
printf("\n");
if((details=fopen(filename, "r+b"))==NULL) {
printf("Cannot open file.\n");
}
else
{
if((details=fopen(filename, "r+b"))!=NULL) {
fread(&filespec , sizeof(struct filedetails), 1,details);
size = sizeof(struct contactinfo);
offset=0;
while(!feof(details))
{
counter +=1;
count +=1;
offset+=size;
if(fseek(details, offset,0)){
printf("Seek error.");
}
else
{
fread(&person, sizeof(struct contactinfo), 1, details);
fprintf(stream,"%i\n",count);
fprintf(stream,"%s\n", person.name);
fprintf(stream,"%s\n", person.number);
fprintf(stream,"%s\n", person.email);
fprintf(stream,"\n");
if(counter == filespec.recnum)break;
}
}
}
}
}
fclose(details);
fclose(stream);
}

A sorted single linked list database written in C

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<malloc.h>
struct addr{
char name[40];
char street[40];
char district[40];
char town[40];
char county[40];
char country[40];
char postcode[40];
char telno[40];
char email[40];
struct addr *next;
};
typedef struct addr address;
address *temp, *start, *pointer,  *i= NULL;

void list(),  add(void),  deletion(void), search(void);
void save(), load(void), txtoutput(void), sort(void);
void readLine(char buffer[]);
int main(void)
{
int choice;
for(;;){
printf("\n");
printf("1.  Insert a record\n");
printf("2.  List the file\n");
printf("3.  Delete a record\n");
printf("4.  Save the file\n");
printf("5.  Save to a text file for output to a wp\n");
printf("6.  Search for a record\n");
printf("7.  Load the file\n");
printf("8.  Quit\n");
do{
printf("\nEnter your choice: ");
scanf("%i",&choice);
getchar();
if(choice==1) add();
if(choice==2) list();
if(choice==3) deletion();
if(choice==4) save();
if(choice==5) txtoutput();
if(choice==6) search();
if(choice==7) load();
if(choice== 8) exit(0);
}while(choice < 1 && choice >8);
}
return 0;
}



void add()
{
address *q;
pointer = (address*) malloc(sizeof(address));
q = (address*) malloc(sizeof(address));
printf("Enter information on new customer\n");

printf("Enter name: ");
readLine(pointer->name);

printf("Enter street: ");
readLine(pointer->street);

printf("Enter district / parish: ");
readLine(pointer->district);

printf("Enter town / city: ");
readLine(pointer->town);

printf("Enter county: ");
readLine(pointer->county);

printf("Enter country: ");
readLine(pointer->country);

printf("Enter postcode: ");
readLine(pointer->postcode);

printf("Enter telephone number: ");
readLine(pointer->telno);

printf("Enter email address: ");
readLine(pointer->email);
if (start == NULL || strcmp(pointer->name, start->name)<0)
{
pointer->next=start;
start=pointer;
}
else
{
q = start;
while(q->next!=NULL && strcmp(q->next->name , pointer->name) < 0)
q=q->next;
pointer->next=q->next;
q->next=pointer;
}
}



void list()
{

if(start==NULL)
printf("No records to view");
/*for (temp=start;temp!=NULL;temp=temp->next)*/
temp = start;
while(temp!=NULL)
{
printf("\n");
printf("%s\n",temp->name);
printf("%s\n",temp->street);
printf("%s\n",temp->district);
printf("%s\n",temp->town);
printf("%s\n",temp->county);
printf("%s\n",temp->country);
printf("%s\n",temp->postcode);
printf("%s\n",temp->telno);
printf("%s\n",temp->email);
printf("\n");
temp=temp->next;
}
}

void readLine(char buffer[])
{
char character;
int i=0;
do
{
character=getchar();
buffer[i]=character;
++i;
}
while(character !='\n');
buffer[i-1]='\0';
}


void save()
{
FILE *fp;
if((fp=fopen("maillist", "wb"))==NULL) {
printf("Cannot open file.\n");
return;
}
temp=start;
while(temp){
fwrite(temp,
sizeof(struct addr), 1, fp);
temp = temp->next;
}
fclose(fp);
}

void load()
{
FILE *fp;
if((fp=fopen("maillist", "rb"))==NULL) {
printf("Cannot open file,\n");
return;
}
start = ( address*) malloc(sizeof(address));
/*while(start){
temp=start->next;
free(temp);
start=temp;
}*/

free(start);
start=NULL;
while(!feof(fp)){

i = ( address*) malloc(sizeof(address));
temp = ( address*) malloc(sizeof(address));
if(!i){
printf("Out of memory.\n");
return;
}
if(1!=fread(i,sizeof(struct addr),1,fp))break;

if(start!=NULL)
{
temp = start;
while(temp->next!=NULL)
temp=temp->next;
i->next=NULL;
temp->next=i;
}
else
{
start=i;
i->next=NULL;
}
}
fclose(fp);
}

void txtoutput(void)
{
int t;
int count;
FILE *stream;
char filename[30];
count = 0;
printf("Enter a file name.\n");
scanf("%s",filename);
printf("\n");
stream = fopen(filename, "w+");
temp = start;
while(temp) {
count = count +1;
fprintf(stream,"%i\n",count); 
fprintf(stream,"%s\n", temp->name);
fprintf(stream,"%s\n", temp->street);
fprintf(stream,"%s\n", temp->district);
fprintf(stream,"%s\n", temp->town);
fprintf(stream,"%s\n", temp->county);
fprintf(stream,"%s\n", temp->country);
fprintf(stream,"%s\n", temp->postcode);
fprintf(stream,"%s\n", temp->telno);
fprintf(stream,"%s\n", temp->email);
fprintf(stream,"\n");
temp=temp->next;
}
fclose(stream);
return;
}

void search()
{
int flag=0;
char name[40]; 
printf("Enter name of person to search for\n");
readLine(name);
temp=start;
while(temp)
{
if(strcmp(name, temp->name)==0)
{
printf("%s\n",temp->name);
printf("%s\n",temp->street);
printf("%s\n",temp->district);
printf("%s\n",temp->town);
printf("%s\n",temp->county);
printf("%s\n",temp->country);
printf("%s\n",temp->postcode);
printf("%s\n",temp->telno);
printf("%s\n",temp->email);
flag= 1;
}
temp=temp->next;
}
if(flag==0) 
printf("Not found in list\n");
}

void deletion()
{
 address *t, *pt;
t = ( address*) malloc(sizeof(address));
pt = ( address*) malloc(sizeof(address));
char name[40];
if(start == NULL)
{
printf("List is empty\n");
return;
}
printf("Enter name of person to be deleted\n");
readLine(name);
if(strcmp(name,start->name)==0)
{
temp=start;
start = start->next;
free(temp);
printf("Record is deleted\n");
return;
}
pt=start;
t=start->next;
while(t!=NULL&& strcmp(t->name,name)!=0)
{
pt =t;
t=t->next;
}
if(t==NULL)
{
printf("Record does not exist\n");
return;
}
if(strcmp(t->name,name)==0)
{
pt->next=t->next;
printf("Record is deleted\n");
free(t);
return;
}
}