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Program is skipping fgets without allowing input
(2 answers)
scanf() leaves the newline character in the buffer
(7 answers)
Closed 3 years ago.
I am very new to C. Trying to practice with input and output now. I am trying to use fgets to read in a sentence and convert it to all upper case letters, but for some reason it's not reading it. I HAVE ADDED *c in MY SCANF AND IT STILL DOES NOT WORK. Any suggestions and tips are greatly appreciated! Thanks in advance.
#include <stdio.h>
#include <ctype.h>
#define ARR_SIZE 100
void modify(int pInt[100], int input);
void modify2(char *pString[100]);
int main() {
printf("Enter a size for your array:\n");
int input;
scanf("%d", &input);
printf("Great! You now have an array of size %d.\n", input);
int array[ARR_SIZE];
printf("Now please enter %d numbers.\n", input);
int i;
for (i = 0; i < input; i++) {
scanf("%d*c", &array[i]);
}
printf("Awesome. All %d slots in the array are now filled.\n", input);
printf("Here is how your array looks:\n");
int j;
for (j = 0; j < input; j++) {
printf(" %d |", array[j]);
}
printf("\n");
modify(array, input);
printf("Now your array looks like this:\n");
for (j = 0; j < input; j++) {
printf(" %d |", array[j]);
}
printf("\n");
printf("Experiment #2:\n");
printf("Enter a sentence:\n");
char sentence[ARR_SIZE];
fgets(sentence, ARR_SIZE, stdin);
modify2(sentence);
printf("Now your sentence is upper case: %s\n", sentence);
return 0;
}
void modify2(char *pString[100]) {
int i = 0;
while (pString[i]) {
pString[i] = toupper(pString[i]);
i++;
}
}
void modify(int pInt[100], int input) {
int i;
for (i = 0; i < input; i++) {
pInt[i] *= 2;
}
}
Related
using namespace std;
int main() {
int input;
int i=0;
while (1){
scanf("%d", &input);
printf("%d input:%d\n", i, input);
i++;
}
}
Stdin Inputs:
10
65
100
30
95
.
.
.
Is there a way to stop the code and escape from while loop after hitting the last Input?
Amount of Inputs can be N.
edition) Is there a way to calculate the amount of Stdin Inputs? This is my major question.
using namespace std;
int main() {
int input;
int i=0;
while (1){
scanf("%d", &input);
printf("%d input:%d\n", i, input);
i++;
if (i >= 5) break; //change 5 to your desired amount of inputs
}
}
Maybe you are reading an input that has an EOF (End of file)?
In that case you should stop when receiving EOF
#include <stdio.h>
#include <ctype.h>
int main(void)
{
int input;
int i = 0;
while (scanf("%d", &input) != EOF){
printf("%d input:%d\n", i, input);
i++;
}
printf("End\n");
return 0;
}
Otherwise you can do a program that first reads N and then iterate N time
int main(void)
{
int input;
int i = 0;
int n = 0;
scanf("%d", &n);
for (i = 0; i < n; i++) {
scanf("%d", &input);
printf("%d input:%d\n", i, input);
}
return 0;
}
#include <stdio.h>
int main() {
int n, i;
char arr[20];
clrscr();
printf("Enter size of array(<=20)");
scanf("%d", &n);
printf("Enter array");
for (i = 0; i < n; i++) {
scanf("%s", &arr[i]);
}
for (i = 0; i < n; i++) {
printf("%s", arr[i]);
}
getch();
return 0;
}
The program does not prints the array
and instead shows
Program termination message
The image shows the program termiantion message
The problem is with the line
printf("%s", arr[i]);.
If you change this line to
printf("%c", arr[i]);
then it will work because %s is used with character arrays that contain strings
I am just giving the solution for your program termination. Still we can do some modification in your code.
Thanks
Just started learning programming on my own and whilst trying to create an array of characters from user input, using scanf, have hit the wall; the code is as below:
#include <stdio.h>
#define I 5
int main (void) {
char a[I+1] = {a[I+1] = '\0'}, q;
int i;
for(i = 0; i < I; i++) {
printf("Enter an alphabet:\t");
//scanf("%c", &q);
//scanf("%c*\n", &q);
//scanf("%[^\n]", &q);
//scanf("%[a-z, A-Z]", &q);
scanf("%127[^\n]", &q);
a[i] = q;
}
printf("\n");
for(i = 0; i < I; i++) {
printf("Element a[%d] of a[I]:\t%c\n", i, a[i]);
}
printf("And the a[I] string:\t%s\n", a);
return 0;
}
None of the scanf combinations in the above code works: the program either skips input prompt after the first one or does not store response.
How can this be resolved with scanf?
char a[I+1] = {a[I+1] = '\0'} is not valid. Even if it compiles, it is going out of bounds when assigning the '\0' character. The commonly used convention looks more like this instead:
char a[I+1] = {0};
Or simply:
char a[I+1] = {};
That said, q is only 1 char in size, but your scanf() is trying to read a string up to 127 chars into q. So you are going to trash memory. To read a single char at a time, use %c instead:
#include <stdio.h>
#include <string.h>
#define MAX_INPUT 5
int main (void) {
char a[MAX_INPUT+1];
int i, len;
for(i = 0; i < MAX_INPUT; i++) {
printf("Enter an alphabet:\t");
scanf("%c", &a[i]);
}
a[MAX_INPUT] = '\0';
printf("\n");
len = strlen(a);
for(i = 0; i < len; i++) {
printf("Element a[%d]:\t%c\n", i, a[i]);
}
printf("And the a string:\t%s\n", a);
return 0;
}
Or, you can remove the loop and just use a single call to scanf() using "%5[^\n]" as the format string:
#include <stdio.h>
#include <string.h>
#define MAX_INPUT 5
int main (void) {
char a[MAX_INPUT+1];
char fmt[20];
int i, len;
sprintf(fmt, "%%%d[^\n]", MAX_INPUT);
printf("Enter an alphabet:\t");
scanf(fmt, a);
printf("\n");
len = strlen(a);
for(i = 0; i < len; i++) {
printf("Element a[%d]:\t%c\n", i, a[i]);
}
printf("And the a string:\t%s\n", a);
return 0;
}
This works without any warning or error on Cygwin gcc v7.3 with Wall flag:
#include <stdio.h>
#define I 5
int main (void) {
char a[I+1] = {a[I+1] = '\0'},q;
int i;
for(i = 0; i < I; i++) {
printf("Enter an alphabet:\t");
scanf("%c%*c", &q);
a[i] = q;
}
printf("\n");
for(i = 0; i < I; i++) {
printf("Element a[%d] of a[I]:\t%c\n", i, a[i]);
}
printf("And the string a[I]:\t%s\n", a);
return 0;
}
I want to have unknown amount of inputs in a single line. For example, user can input:
"ans: 1 2 3 4 5"
and scanf() will store these five numbers to an array. The problem is that the program don't know how many input will there be.
#include <stdio.h>
int main()
{
int i;
int input[4];
scanf("ans: " for(i = 0, i < 3,i++){scanf(" %d", &input[i]);};
return 0;
}
Sorry I'am totally new to coding, what will be the proper way to write this? Or is this impossible?
Thanks :)
Use fgets() and sscanf() with "%n"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
char input[100];
int arr[10];
//fgets(input, sizeof input, stdin);
strcpy(input, "1 2 42 56 -3 0 2018\n"); // fgets
char *pi = input;
int tmp, pp, i = 0;
while (sscanf(pi, "%d%n", &tmp, &pp) == 1) {
if (i == 10) { fprintf(stderr, "array too small\n"); exit(EXIT_FAILURE); }
pi += pp;
arr[i++] = tmp;
}
printf("got this ==>");
for (int k = 0; k < i; k++) printf(" %d", arr[k]);
puts("");
}
You asked this question way round.
You can achieve what you expect by putting scanf inside of a loop.Even you can ask user to give how many inputs he want to enter.
#include <stdio.h>
int main()
{
int i;
int input[4];
printf("Enter the number of inputs you want to give : ");
scanf("%d", &n);
for(i = 0; i < n;i++)
{
printf("Enter the input number %d : ",i);
scanf("%d", &input[i]);
}
return 0;
}
hi my program is to enter a number which gives the length of the string then the string and then finally a letter which should then tell me how many times that letter is in the string. Currently to help me figure out what is wrong with my code i can see that the strcmp is resulting in the same ascii number but negative. eg for the letter a the number is 97 but the strcmp is giving out -97 so the strcmo doesnt show the character as being in the string and results in the incorrect result. Any help would be greatly appreciated. thanks
#include
#include
int main(void)
{
char myChar[100], z, k;
int counter, n, g=0, r, i, l;
counter=0;
scanf("%d",&n);
while (counter<n)
{
counter++;
scanf(" %c",&myChar[counter]);
}
scanf(" %s", &z);
for(i=0;i<n+1;++i)
{
k=myChar[i];
r=strcmp(&z, &k);
l=r;
//printf("\n%c", myChar[i]);
printf("%d\n", l);
if(r==0)
{
g++;
printf("%d\n", g);
}
}
printf("\n\n%d\n", g);
return (0);
}
#include <stdio.h>
#include <string.h>
int main(void){
char myChar[100], str[64];//
int counter, n;
int i, j, k;
printf("number of charactors : ");
scanf("%d",&n);
for (i=0; i<n; ++i){
scanf(" %c", &myChar[i]);
}
printf("input string : ");
scanf("%63s", str);//"%s" : The useless one letter to input as a string. "%c" for &z
for(i=0;i<n;++i){
counter = 0;
for(j=0;str[j]!='\0'; ++j){
k = (str[j] == myChar[i]);//Comparison of each character
counter += k;//if(str[j] == myChar[i]) ++counter;
}
printf("%c is %d\n", myChar[i], counter);
}
return (0);
}