Updating a record in a binary file

#include<stdio.h> #include<conio.h> #include<stdlib.h> int main() { struct stud { char name[20]; int rollno; char br[20]; }s; int x,z; char name[20]; FILE *fp; fp=fopen("D:\\a.dat","rb+"); if(fp==NULL) { printf("FNF"); exit(); } puts("Enter name name to search"); gets(name); while(1) { x=fread(&s,sizeof(s),1,fp); if(x==0) break; if(strcmp(name,s.name)==0) { printf("\n%s %d %s ",s.name,s.rollno,s.br); puts("enter new date"); printf("Enter name:"); fflush(stdin); gets(s.name); printf("Enter rollno"); fflush(stdin); scanf("%d",&s.rollno); printf("Enter branch"); fflush(stdin); gets(s.br); fseek(fp,-sizeof(s),1); printf("\nold \n%s %d %s ",s.name,s.rollno,s.br); if(fwrite(&s,sizeof(s),1,fp)==1) { printf("Record inserted..."); break; } else { printf("There is some problem"); break; } } } fclose(fp); return 0; } in D drive i have a file a.dat which is having 5 following records ajay 1 cse vijay 2 it raj 3 ETC megha 4 it ramesh 5 cse I want to update a perticular record from a.dat for that i have written the above program but this program is not updating. plz tell me wha ----------------------------------------------------

On 2009-11-16, manish sahu <manish.comp05@gmail.com> wrote: > #include<conio.h> Don't include this, you don't need it and it's not portable. > { struct stud > { > char name[20]; > int rollno; > char br[20]; > > }s; Don't declare structs inside functions. It's bad style. > fflush(stdin); This is undefined behavior; it might coredump, it might blow up, it might do nothing at all... Don't use this. If you think you need this, you should rethink your input. > gets(s.name); Don't use gets, it's unsafe. > fseek(fp,-sizeof(s),1); Don't use a literal as the last argument to fseek, use the predefined constants. > printf("Record inserted..."); You can't "insert" data in standard C, so either you're trying to do something wrong here or this message is incorrect. > in D drive i have a file a.dat which is having 5 following records > ajay 1 cse > vijay 2 it > raj 3 ETC > megha 4 it > ramesh 5 cse Those records do not match the structure you defined. You have defined a structure which has a precise size and layout, but you appear to have records which do not match that size and layout, so of course, it doesn't work. > plz tell me wha There's probably another half-dozen or so things wrong, but the above should get you started. -s -- Copyright 2009, all wrongs reversed. Peter Seebach / usenet-nospam@seebs.net http://www.seebs.net/log/ <-- lawsuits, religion, and funny pictures http://en.wikipedia.org/wiki/Fair_Game_(Scientology) <-- get educated!

Seebs wrote: > On 2009-11-16, manish sahu <manish.comp05@gmail.com> wrote: >>{ struct stud >> { >> char name[20]; >> int rollno; >> char br[20]; >> >> }s; > > > Don't declare structs inside functions. It's bad style. This is the first I've ever heard of structs being something which shouldn't be declared inside of functions. That makes no sense to me. void q1sort(void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *)) { unsigned char *left; size_t middle, last, right; struct { size_t bytes; void *base; } stack[CHAR_BIT * sizeof nmemb], *stack_ptr; unsigned char *p1, *p2, *end, swap; stack -> bytes = nmemb * size; stack -> base = base; stack_ptr = stack + 1; do { --stack_ptr; if (stack_ptr -> bytes > size) { left = stack_ptr -> base; right = stack_ptr -> bytes - size; last = middle = 0; do { middle += size; if (compar(left, left + middle) > 0) { last += size; p1 = left + middle; p2 = left + last; end = p2 + size; do { swap = *p1; *p1++ = *p2; *p2++ = swap; } while (p2 != end); } } while (middle != right); p1 = left; p2 = left + last; end = p2 + size; do { swap = *p1; *p1++ = *p2; *p2++ = swap; } while (p2 != end); if (right - last > last) { stack_ptr -> base = left + last + size; stack_ptr++ -> bytes = right - last; stack_ptr -> base = left; stack_ptr++ -> bytes = last; } else { stack_ptr++ -> bytes = last; stack_ptr -> base = left + last + size; stack_ptr++ -> bytes = right - last; } } } while (stack_ptr != stack); } -- pete

In article <Re6dnamKBJy2mJzWnZ2dnUVZ_rednZ2d@earthlink.com>, pete <pfiland@mindspring.com> wrote: >> Don't declare structs inside functions. It's bad style. >This is the first I've ever heard of structs >being something which shouldn't be declared inside of functions. I'd say don't declare struct types *unnecessarily* within functions. That's because it's generally more readable to keep the function itself short. And of course it rarely arises, because the vast majority of struct types are shared between several functions. If a struct type is genuinely private to a function, and you have a lot of such functions in one file, then restricting its scope by declaring it within the function saves you from having to invent a bunch of different names. -- Richard -- Please remember to mention me / in tapes you leave behind.

On 2009-11-16, pete <pfiland@mindspring.com> wrote: > Seebs wrote: >> Don't declare structs inside functions. It's bad style. > This is the first I've ever heard of structs > being something which shouldn't be declared inside of functions. It's *usually* the case -- because an object like a data record would usually be accessed from other functions too. As with most rules, it is a rule that you eventually learn when to break. -s -- Copyright 2009, all wrongs reversed. Peter Seebach / usenet-nospam@seebs.net http://www.seebs.net/log/ <-- lawsuits, religion, and funny pictures http://en.wikipedia.org/wiki/Fair_Game_(Scientology) <-- get educated!

On Nov 15, 11:15=A0pm, manish sahu <manish.com...@gmail.com> wrote: > #include<stdio.h> > #include<conio.h> > #include<stdlib.h> > int main() > { =A0 =A0 =A0struct stud > =A0 =A0 =A0 =A0 { > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 char name[20]; > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 int rollno; > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 char br[20]; > > =A0 =A0 =A0 =A0 }s; > =A0 =A0 =A0 =A0 int x,z; > =A0 =A0 =A0 =A0 char name[20]; > =A0 =A0 =A0 =A0 FILE *fp; > =A0 =A0 =A0 =A0 fp=3Dfopen("D:\\a.dat","rb+"); > =A0 =A0 =A0 =A0 if(fp=3D=3DNULL) > =A0 =A0 =A0 =A0 { > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 printf("FNF"); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 exit(); > =A0 =A0 =A0 =A0 } > =A0 =A0 =A0 =A0 puts("Enter name name to search"); > =A0 =A0 =A0 =A0 gets(name); > =A0 =A0 =A0 =A0 while(1) > =A0 =A0 =A0 =A0 { > =A0 =A0 =A0 =A0 =A0 =A0x=3Dfread(&s,sizeof(s),1,fp); > =A0 =A0 =A0 =A0 =A0 =A0if(x=3D=3D0) > =A0 =A0 =A0 =A0 =A0 =A0break; > =A0 =A0 =A0 =A0 =A0 =A0 if(strcmp(name,s.name)=3D=3D0) > =A0 =A0 =A0 =A0 =A0 =A0 { > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 printf("\n%s =A0 =A0%d =A0%s ",s.name,s.r= ollno,s.br); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 puts("enter new date"); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 printf("Enter name:"); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 fflush(stdin); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 gets(s.name); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 printf("Enter rollno"); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 fflush(stdin); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 scanf("%d",&s.rollno); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 printf("Enter branch"); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 fflush(stdin); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 gets(s.br); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 fseek(fp,-sizeof(s),1); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 printf("\nold \n%s =A0 =A0%d =A0%s ",s.na= me,s.rollno,s.br); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 if(fwrite(&s,sizeof(s),1,fp)=3D=3D1) > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 { > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 printf("Record =A0inserte= d..."); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 break; > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 } > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 else > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 { > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 printf("There is some pro= blem"); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 break; > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 } > > =A0 =A0 =A0 =A0 =A0 =A0 } > =A0 =A0 =A0 =A0 } > =A0 =A0 =A0 fclose(fp); > =A0 =A0 =A0 return 0; > > } > > in D drive i have a file a.dat =A0which is having 5 following records > ajay 1 cse > vijay 2 it > raj =A0 3 =A0ETC > megha 4 it > ramesh 5 cse > > I want to update a perticular record from a.dat > for that i have written the above program but this program is not > updating. > plz tell me wha > ---------------------------------------------------- HTH: #include<stdio.h> #include<stdlib.h> #include<string.h> char*q0(char*q1, int q2)??<char*q3=3Dq1, *q4; if ((q1=3D=3DNULL)||(q2<1))q3=3DNULL ; else if (q2=3D=3D1)*q3=3D'\0'; else if ((q3=3Dfgets(q1, q2, stdin))!=3DNULL)if ((q4=3D strchr(q1, '\n')))*q4=3D'\0'; return q3; ??>typedef struct q5??<char q6??( 20??); int q7; char q8??(20??); ??>q9; void q10()??<static const q9 q11??( ??)=3D??<??< "\141\152\141\171", 1, "\143\163\145"??>, ??< "\166\151\152\141\171", 2, "\151\164"??>, ??< "\162\141\152", 3, "\105\124\103"??>, ??< "\155\145\147\150\141", 4, "\151\164"??>, ??< "\162\141\155\145\163\150", 5, "\143\163\145"??>, ??>; FILE*q12=3Dfopen( "\141\56\144\141\164", "\167\142\53"); if (q12)??<size_t q13; for (q13=3D0;q13<sizeof q11/sizeof q11??(0??);q13++)??<size_t q2=3D fwrite(&q11??(q13??), sizeof q11??(0??), 1, q12); if (q2!=3D1)??<perror( "\106\151\154\145\40\167\162\151\164\145\40\160\162\157\142\154" "\145\155\56" ); exit(EXIT_FAILURE); ??>??>??>else??<perror( "\106\151\154\145\40" "\157\160\145\156\40\160\162\157\142\154\145\155\40\157\156\40" "\106\151\154\145\72\141\56\144\141\164\56" ); exit(EXIT_FAILURE); ??>fclose(q12); ??>void q14(q9 q15, char*q16)??< printf( "\45\163\76\40\156\141\155\145\75\45\163\54\40\162\157\154\154" "\156\157\75\45\144\54\40\142\162\141\156\143\150\75\45\163\n", q16, q15.q6, q15.q7, q15.q8); ??>int main(int q17, char**q18)??<q9 q15; int q19; static const size_t q20=3Dsizeof q15; const long q21=3D(int)q20; char q6??( 20??); FILE*q22; char q23??(FILENAME_MAX??)=3D"\141\56\144\141\164"; if (q17 >1)??<strncpy(q23, q18??(1??), sizeof q23); ??>q22=3Dfopen(q23, "\162\142\53"); if (q22=3D=3DNULL)??<q10(); q22=3Dfopen( "\141\56\144\141\164", "\162\142\53"); if (q22=3D=3DNULL)??<perror( "\111\57\117\40\160\162\157\142\154\145\155"); printf( "\125\156\141" "\142\154\145\40\164\157\40\157\160\145\ \156\40\45\163\n", q23); exit(EXIT_FAILURE); ??>??>puts( "\105\156\164" "\145\162\40\156\141\155\145\40\156\141\155\145\40\164\157\40\163" "\145\141\162\143\150" ); q0(q6, sizeof q6); for (;;)??<q19=3Dfread(&q15, sizeof(q15), 1, q22); if (q19 =3D=3D0)break; if (strcmp(q6, q15.q6)=3D=3D0)??<char q24??(15??); q14(q15, "\146\157\165\156\ \144\72\40"); puts( "\75\75\75\75\75\75\75\75\75\75\75\75\75\75"); puts( "\105\156\164\145\162\40\156\145\167\40\144\141\164\141"); puts( "\75\75\75\75\75\75\75\75\75\75\75\75\75\ \75"); printf( "\105\156\164\145\162\40\156\141\155\145\72"); fflush( stdout); q0(q15.q6, sizeof q15.q6); printf( "\105\156\164\145\162\40\162\157\154\154\156\157\72"); fflush(stdout); q0(q24, sizeof q24); sscanf(q24, "\45\144", &q15.q7); printf( "\105\156\164\145\162\40\142\162\141\156\143\150\72"); fflush(stdout); q0(q15.q8, sizeof q15.q8); fseek(q22, -q21, SEEK_CUR); printf( "\n\157\154\144\40\n\45\163\40\40\40\40\45\144\40\40\45\163\40", q15.q6 , q15.q7, q15.q8); if (fwrite(&q15, sizeof(q15), 1, q22)=3D=3D1)??<printf( "\122" "\145\143\157\162\144\40\162\145\167\162\151\164\164\145\156\56\56" "\56" ); break; ??>else??<perror( "\124\150\145\162\145\40\151\163\40\163\157" "\155\145\40\160\162\157\142\154\145\155\40\162\145\167\162\151\164" "\151\156\147\40\162\145\143\157\162\144\56" ); break; ??>??>else??<q14(q15, "\163\153\151\160\160\151\156\147\ \72\40"); ??>??>fclose(q22); return 0; ??>