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Search found 278 results on 12 pages for 'scanf'.

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• segmentation fault

  - by gcc

  int num_arrays; char *p[20]; char tempc; int i=0; do { p[i]=malloc(sizeof(int)); scanf("%s",p[i]); tempc=p[i]; ++i; }while(tempc=='x'); num_arrays=atoi(p[0]); When i write num_arrays=atoi(..),gcc give me segmentation fault or memory stack is exceeded, I don't understand why it behaves like that can anyone explain, why?

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• How does this iterative Tower of Hanoi work? C

  - by Nitesh Panchal

  Hello, while surfing google, i found this interesting solution to Tower Of Hanoi which doesn't even use stack. Can anybody explain me in brief, what is it actually doing? And this solution really acceptable? #include <stdio.h> #include <stdlib.h> int main() { int n, x; printf( "How many disks? " ); scanf( "%d", &n ); printf("\n"); for (x=1; x < (1 << n); x++) printf( "move from tower %i to tower %i.\n", (x&x-1)%3, ((x|x-1)+1)%3 ); return 0; }

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• If free() knows the length of my array, why can't I ask for it in my own code?

  - by Chris Cooper

  I know that it's a common convention to pass the length of dynamically allocated arrays to functions that manipulate them: void initializeAndFree(int* anArray, int length); int main(){ int arrayLength = 0; scanf("%d", &arrayLength); int* myArray = (int*)malloc(sizeof(int)*arrayLength); initializeAndFree(myArray, arrayLength); } void initializeAndFree(int* anArray, int length){ int i = 0; for (i = 0; i < length; i++) { anArray[i] = 0; } free(anArray); } but if there's no way for me to get the length of the allocated memory from a pointer, how does free() "automagically" know what to deallocate? Why can't I get in on the magic, as a C programmer? Where does free() get its free (har-har) knowledge from?

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• C - 3rd line on a txt

  - by Pedro

  Hi....I have on the txt file this: Hello Experience 3 Bad Hi want to scanf the 3rd line; i'm doing this: FILE *fp; int number; fp=fopen("test.txt","r"); if(fp==NULL){ printf("Error\n"); } while(!feof(fp)){ for(i=0;i<=3;i++){ if(i==3){ fscnaf(number,fp); prinf("string in the 3rd line is %s\n",number); } } } system("PAUSE"); } I need to use the fscanf, because i will need it, the number is the size of students in a school... Something is wrong, but i don't know what is...please help me...

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• Can someone explain how pointer to pointer works?

  - by user3549560

  I don't really understand how the pointer to pointer works. Any way to do the same work without using pointer to pointer? struct customer{ char name[20]; char surname[20]; int code; float money; }; typedef struct customer customer; void inserts(customer **tmp) { *tmp = (customer*)malloc(sizeof(customer)); puts("Give me a customer name, surname code and money"); scanf("%s %s %d %f", (*tmp)->name, (*tmp)->surname, &(*tmp)->code,&(*tmp)->money); }

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• How to add characters to reach the maximum size of a char[].

  - by Bon_chan

  Hi folks, I have the following part of code : for(int i=0;i<n;i++) { printf("Student %d\n",i+1); printf("Enter name : "); scanf("%s",&(student+i)->name); fflush(stdin); lengthName = strlen((student+i)->name); while(lengthName !='\0') { }} when the length is shorter than 10, it will add hyphens until reaching the maximum size. Ex : John = 6 hyphens will be added I know how to do it in csharp but can't figure it out in c. Could some of you give me some lights please? PS : Oh yes the variable name is char name[10+1] and it a part of the structure called student.

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• C : Memory layout of C program execution

  - by pavun_cool

  Hi All , I wanted know how the kernel is providing memory for simple C program . For example : #include<stdio.h> #include<malloc.h> int my_global = 10 ; main() { char *str ; static int val ; str = ( char *) malloc ( 100 ) ; scanf ( "%s" , str ) ; printf( " val:%s\n",str ) ; } See, In this program I have used static , global and malloc for allocating dynamic memory So , how the memory lay out will be ... ? Any one give me url , which will have have details information about this process..

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• stack of a c program

  - by ckarthickit

  how the stack would look like for the following program if I give input as 5. #include <stdio.h> int fibonacci(int number) { int retval; if (0 == number){ return 0; } if (1 == number){ return 1; } return(fibonacci(number-1) + fibonacci(number-2)); } int main() { int number = 0; int fibvalue = 1; while (1){ printf("please enter the number\n"); scanf("%d", &number); fibvalue = fibonacci(number); printf("computed fibonacci value %d\n", fibvalue); } return 1; } also give me links where i can learn about it

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• problem with threads

  - by Nadeem

  i want to be done for 10 times!!, to scan teh number and print it again!!, how i can do that #include <stdio.h> #include <pthread.h> #include <semaphore.h> sem_t m; int n; void *readnumber(void *arg) { scanf("%d",&n); sem_post(&m); } void *writenumber(void *arg) { //int x =3; //while(x>0) //{ //x = x-1; sem_wait(&m); printf("%d",n); //} } int main(){ pthread_t t1, t2; sem_init(&m, 0, 0); pthread_create(&t2, NULL, writenumber, NULL); pthread_create(&t1, NULL, readnumber, NULL); pthread_join(t2, NULL); pthread_join(t1, NULL); sem_destroy(&m); return 0; }

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• Allocating memory in char * struct

  - by mrblippy

  hi, im trying to read in a word from a user, then dynamically allocate memory for the word and store it in a struct array that contains a char *. i keep getting a implicit declaration of function âstrlenâ so i know im going wrong somewhere. struct class { char class_code[7]; char *name; }; char buffer[101]; struct unit units[1000]; scanf("%s", buffer); units[0].name = (char *) malloc(strlen(buffer)+1); strcpy(units[0].name, buffer);

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• Allocating memory for a char pointer that is part of a struct

  - by mrblippy

  hi, im trying to read in a word from a user, then dynamically allocate memory for the word and store it in a struct array that contains a char *. i keep getting a implicit declaration of function âstrlenâ so i know im going wrong somewhere. struct class { char class_code[4]; char *name; }; char buffer[101]; struct unit units[1000]; scanf("%s", buffer); units[0].name = (char *) malloc(strlen(buffer)+1); strcpy(units[0].name, buffer);

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• Why do i get segfault at the end of the application after everything's beed done properly ?

  - by VaioIsBorn

  #include <string.h> #include <stdlib.h> #include <stdio.h> int main(void) { unsigned char *stole; unsigned char pass[] = "m4ak47"; printf("Vnesi password: \t"); scanf("%s", stole); if(strncmp(stole, pass, sizeof(pass)) != 0) { printf("wrong password!\n"); exit(0); } else printf("Password correct\n"); printf("some stuf here...\n\n"); return 0; } This program is working nice, but with one problem - if the password is correct then it DOES do the printing of 'some stuf here...' but it also shows me segmentation fault error at the end. Why ?

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• In OCaml, how can I create an out_channel which writes to a string/buffer instead of a file on disk

  - by Tianyi Cui

  I have a function of type in_channel -> out_channel -> unit which will output something to an out_channel. Now I'd like to get its output as a string. Creating temporary files to write and read it back seems ugly, so how can I do that? Is there any other methods to create out_channel besides Pervasives.open_out family? Actually, this function implemented a repl. What I really need is to test it programmatically, so I'd like to first wrap it to a function of type string -> string. For creating the in_channel, it seems I can use Scanf.Scanning.from_string, but I don't know how to create the out_channel parameter.

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• How to prevent users from typing incorrect inputs ?

  - by ZaZu

  Hello, I want the program to loop a scan function if the user types anything else other than numbers.. My code is : do{ printf("Enter rows\n"); scanf("%d",&row); }while(row>='a' && row<='z'); but this code doesnt work .. I keep getting an error when typing in a letter. I tried manipulating around it and the whole thing loops infinitely ... What am I doing wrong ? Please help thanks !

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• a newbie gcc compiler and c language question

  - by dydx

  Hi, when I'm trying to compile my c program it gives me this error warning: integer constant is too large for 'long' type which refers to these lines int barcode, a, b, c; scanf("%d", &barcode); a = barcode / 1000000000000; b = barcode / 100000000000 % 10; c = barcode / 10000000000 % 10; and the rest is fine. I know I'm not supposed to use int for such a large number, any suggestions on what I should use? if I replace int with double what should the '%d' part be replaced with then?

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• collect string in loop and printout all the string outside loop

  - by user1508163

  I'm newbie here and there is some question that I want have some lesson from you guys. For example: #include <stdio.h> #include<stdlib.h> #include<ctype.h> void main() { char name[51],selection; do { printf("Enter name: "); fflush(stdin); gets(name); printf("Enter another name?(Y/N)"); scanf("%c",&selection); selection=toupper(selection); }while (selection=='Y'); //I want to printout the entered name here but dunno the coding printf("END\n"); system("pause"); } As I know when the loops perform will overwrite the variable then how I perform a coding that will printout all the name user entered? I have already ask my tutor and he is ask me to use pointer, can anyone guide me in this case?

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• Create a basic matrix in C (input by user !)

  - by DM

  Hi there, Im trying to ask the user to enter the number of columns and rows they want in a matrix, and then enter the values in the matrix...Im going to let them insert numbers one row at a time. How can I create such function ? #include<stdio.h> main(){ int mat[10][10],i,j; for(i=0;i<2;i++) for(j=0;j<2;j++){ scanf("%d",&mat[i][j]); } for(i=0;i<2;i++) for(j=0;j<2;j++) printf("%d",mat[i][j]); } This works for inputting the numbers, but it displays them all in one line... The issue here is that I dont know how many columns or rows the user wants, so I cant print out %d %d %d in a matrix form .. Any thoughts ? Thanks :)

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• I make this for balancing paranthesis of equation but i think it is wrong check and correct it

  - by muhammadlodhi

  int main(){ char i,input[30],close,open; for(i=0;i<='.';i++){ printf("enter equation"); scanf("%c",input[i]); if(input[i]=='(') input++; input[i]=open; else if(input[i]==')') input[i]--; input[i]=close; else if(open[i]==close[i]) { printf("paranthesis are balance"); } else printf("paranthesis are not balance"); } getch(); return 0; }

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• Whats wrong with this C program?

  - by Prab

  It should give me the number of inputs entered by the user. But it gives 100. I compiled with gcc. #include <stdio.h> int arr[100]; int count=0; int max=100; int main(){ int i, input; printf("Enter integer values one by one, q to quit.\n"); for(i=0;i<max;i++){ scanf("%d",&input); arr[i]=input; if(input=='q')break; count++; } printf("You entered %d values.\n",count); return 0; }

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• Enter custom file name to be read ?

  - by ZaZu

  Hello, I want to allow users to type the name of any .txt file to be read/written. This is my code : printf("Enter .txt file name\n"); scanf("%s",&fname); FILE *inputf; inputf=fopen(&fname,"w"); Problem is this method does not work (having &fname) as a parameter. I can imagine its because C needs "filename.txt" for it work ... even if I enter for example : "custom.txt", the program returns an error of "Storage block not big enough for this operation" What is the correct method to accomplish this ? Im using C and im pretty much using basic commands .. (not too advanced) Thanks alot !!!

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• creating new array according to input

  - by gcc

  int *arrays[20],j,a=0; /*int num_arrays;*/ char *tutar[200]; int /*fe*/i=0,n,temp; do{ tutar[i]=malloc(sizeof(int)); scanf("%s",tutar[i]); temp=*tutar[i]; ++i; } while(temp!='x'); int *arrays[20],j,a=0; n=i; j=1; for(i=1;i if(atoi(tutar[i])=='n') { ++j; arrays[j]=malloc(sizeof(int)); a=0; } arrays[j][a]=*(int *)tutar[i]; if(atoi(tutar[i])=='x') break; } input: 1 2 3 4 n 14 23 39 n 98 100 x output: arrays[1]:2 3 4 arrays[2]:14 23 39 arrays[3]:98 100 //i wanna output like that but my code didnt give me output like that //can anyone fix my code or (explain where is my error)

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• Checking for an "end of line" in a C-string

  - by Numerator

  I would really love your help with the following problem: I want to get as an input from the user a maximum length of 30 chars string and check whether it contains an end of line. This is what I tried to write so far: int main(void) { int i; char* command = (char*)calloc(31, sizeof(char)); while (0 < 1) { scanf("%s", command); for (i = 0; i <= strlen(command); ++i) { if (command[i] == '\n') printf("here"); } if (strcmp(command, "quit") == 0) break; } The idea is to check whether the command given by the user as input is "legal" - that is of length < 31. when i run this code, it never prints "here" regardless of the length of input.

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• dimension || pointer pointer

  - by gcc

  What are pointers to pointers (like char **p;) used for? Can there be char ***p; or char ****p;? What would they be used for? my real question is >>what is the main purpose of char **p; why we need to use that type one answer is char *p - one dimension char *p - 2 dimensions char **p - 3 dimensions i have asked you can give example but he havenot answer i am thinking can we use ? is p[i][j] to **p that is can we use it like for(;;) for(;;) scanf("....",p[i][j]);

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• sorting set of five string in alphabetical oder throwing warning?

  - by rost rost

  sorting set of five string in alphabetical oder throwing warning ?my code is below please help me to fix it #include<stdio.h> #include<string.h> int main() { char a[5][20],t[20]; int i,j; printf("enter 5 string\n") scanf("%s",a); for(i=1;i<5;i++) { for(j=1;j<5;j++) { if(strcmp(a[j-1],a[j])>0) { strcpy (t,a[j-1]); strcpy (a[j-1],a[j]); strcpy(a[j],t); } } } for(i=1;i<5;i++) printf("%s\n",a[i]); } ~

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• what wrong are there

  - by gcc

  int main(void) { char *tutar[100][20],temp; int i; int n; i=0; while(temp!='x') { scanf("%c",&temp); tutar[i]=malloc(sizeof(int)); tutar[i]=temp; ++i; } n =i; for(i=0;i<=n;++i) { printf(" %c ",*tutar[i]); } printf("\n\n"); /*for(i=0;i<=n;++i) { printf("%d",atoi(*tutar[i])); } */

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