This code works well for words with less than five letters: (but not for higher)
#include <stdio.h>
int main(void)
{
const int size = 5;
char str1[size], str2[size], str3[size];
printf("Type word1: ");
scanf("%s", str1);
printf("Type word2: ");
scanf(" %s", str2);
printf("Type word3: ");
scanf(" %s", str3);
printf("First chars: '%c', '%c' e '%c'.\n", str1[0], str2[0], str3[0]);
return 0;
}
The only way to run correctly would increase the 'size' variable? I wonder if it is possible to work properly with larger words without necessarily increasing the 'size' variable.
This will get you close
Just save 1st char
#include <stdio.h>
int main(void)
{
char str[3];
printf("Type word1: ");
scanf(" %c%*s", &str[0]);
printf("Type word2: ");
scanf(" %c%*s", &str[1]);
printf("Type word3: ");
scanf(" %c%*s", &str[2]);
printf("First chars: '%c', '%c' e '%c'.\n", str[0], str[1], str[2]);
return 0;
}
regarding this kind of line: 'scanf("%s", str1);'
1) the scanf format string needs to limit the number of characters input,
otherwise (in this case)
inputting a word longer than 4 char will result in a buffer overrun
2) always check the returned value from scanf
to assure the input/conversion operation was successful.
3) I would strongly suggest using fgets() and sscanf()
then
--the max number of characters is limited by a fgets() parameter,
--the string is null terminated,
--the newline is part of the string,
so will need to be overlayed with '\0'
4) in the user prompts,
I would use:
printf( "\nUsing %d or less characters, enter a string:", argv[1] );
where argv[1] is a command line parameter that indicates the max string length.
(be sure to allow for the nul terminator byte)
Related
I'm trying to get the difference of two characters.
My problem is when I input the 2nd character it gives a different value even if the character is just the same as the first input:
Example below. I input "a" as first char and then "a" again for the second but it gives different value
int main(){
char* flet;
char* slet;
printf("Input first character:");
scanf("%c", &flet);
fflush(stdin);
printf("Input Second character:");
scanf("%c", &slet);
printf("First Char is \"%c\" and Second Char is \"%c\".", flet,slet);
DiffofChar(flet,slet);
}
void DiffofChar(char* letter1, char* letter2){
int theDiff;
theDiff = letter1 - letter2;
printf("The difference of %c (%d) and %c (%d) is %d.", letter1, letter1, letter2, letter2, theDiff);
}
Output:
This is incorrect:
char* flet;
char* slet;
printf("Input first character:");
scanf("%c", &flet);
At best, the above will cast the character value typed (a) into a pointer and that address (0x61 == 'a') will just be a pointer value for an invalid memory location.
The fix is to declare the variables as just type char. You still pass &flet and &slet to the scanf functions.
char flet;
char slet;
printf("Input first character:");
scanf("%c", &flet);
I have a for loop, which I want to get the input from the user and print the associated ascii value. But it only asks for the user input in the second iteration, which is followed and preceded by the output 10. I tried to get rid of new-line characters, but it still prints out 10.
#include <stdio.h>
int main(void){
int number;
printf("Enter the number:");
scanf("%i", &number);
for( ; number > 0; number--){
char character;
printf("Give a char: \n");
scanf("%c", &character);
printf("The associated ascii value is %i \n", character);
}
return 0;
}
Maybe simpler (though using scanf() for user input is not recommended)
scanf(" %c", &character);
// ^ skip otional leading whitespace
Your whole program using fgets() for user input (and my indentation, spacing, style; sorry)
#include <stdio.h> // printf(), fgets()
#include <stdlib.h> // strtol()
int main(void) {
int number;
char buffer[100]; // space enough
printf("Enter the number:");
fgets(buffer, sizeof buffer, stdin);
number = strtol(buffer, 0, 10); // error checking missing
for (; number > 0; number--) {
printf("Give a char: ");
fgets(buffer, sizeof buffer, stdin); // reuse buffer, error checking missing
if (buffer[0] != '\n') {
printf("The associated ascii value of '%c' is %i.\n", *buffer, *buffer);
}
}
return 0;
}
This should solve your problem. getchar() will read the extra newline character from buffer.
#include <stdio.h>
int main(void){
int number;
printf("Enter the number:");
scanf("%i", &number);
for( ; number > 0; number--){
char character;
printf("Give a char: ");
getchar();
scanf("%c", &character);
printf("The associated ascii value is %i \n", character);
}
return 0;
}
regarding;
scanf("%c", &character);
the first time through the loop the '\n' is input.
on all following passes through the loop, the scanf() fails, so the value in character does not change.
This is a prime example of why your code should be error checking.
for instance, to error check the call to scanf():
if( scanf("%c", &character) != 1 )
{
fprintf( stderr, "scanf for a character failed\n" );
break;
}
the 1 is because the scanf() family of functions returns the number of successful: input format conversion specifiers or EOF and it is best to assure the 'positive' status.
I'm pretty new to C, and I have a problem with inputing data to the program.
My code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
int a;
char b[20];
printf("Input your ID: ");
scanf("%d", &a);
printf("Input your name: ");
gets(b);
printf("---------");
printf("Name: %s", b);
system("pause");
return 0;
}
It allows to input ID, but it just skips the rest of the input. If I change the order like this:
printf("Input your name: ");
gets(b);
printf("Input your ID: ");
scanf("%d", &a);
It will work. Although, I CANNOT change order and I need it just as-is. Can someone help me ? Maybe I need to use some other functions. Thanks!
Try:
scanf("%d\n", &a);
gets only reads the '\n' that scanf leaves in. Also, you should use fgets not gets: http://www.cplusplus.com/reference/clibrary/cstdio/fgets/ to avoid possible buffer overflows.
Edit:
if the above doesn't work, try:
...
scanf("%d", &a);
getc(stdin);
...
scanf doesn't consume the newline and is thus a natural enemy of fgets. Don't put them together without a good hack. Both of these options will work:
// Option 1 - eat the newline
scanf("%d", &a);
getchar(); // reads the newline character
// Option 2 - use fgets, then scan what was read
char tmp[50];
fgets(tmp, 50, stdin);
sscanf(tmp, "%d", &a);
// note that you might have read too many characters at this point and
// must interprete them, too
scanf will not consume \n so it will be taken by the gets which follows the scanf. flush the input stream after scanf like this.
#include <stdlib.h>
#include <string.h>
int main(void) {
int a;
char b[20];
printf("Input your ID: ");
scanf("%d", &a);
fflush(stdin);
printf("Input your name: ");
gets(b);
printf("---------");
printf("Name: %s", b);
system("pause");
return 0;
}
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
int a;
char b[20];
printf("Input your ID: ");
scanf("%d", &a);
getchar();
printf("Input your name: ");
gets(b);
printf("---------");
printf("Name: %s", b);
return 0;
}
Note:
If you use the scanf first and the fgets second, it will give problem only. It will not read the second character for the gets function.
If you press enter, after give the input for scanf, that enter character will be consider as a input f or fgets.
you should do this way.
fgetc(stdin);
scanf("%c",&c);
if(c!='y')
{
break;
}
fgetc(stdin);
to read input from scanf after reading through gets.
scanf("%d", &a); can't read the return, because %d accepts only decimal integer. So you add a \n at the beginning of the next scanf to ignore the last \n inside the buffer.
Then, scanf("\n%s", b); now can reads the string without problem, but scanf stops to read when find a white space. So, change the %s to %[^\n]. It means: "read everthing but \n"
scanf("\n%[^\n]", b);
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
int a;
char b[20];
printf("Input your ID: ");
scanf("%d", &a);
printf("Input your name: ");
scanf("\n%[^\n]", b);
//first \n says to ignore last 'return'
//%[^\n] read until find a 'return'
printf("---------\n");
printf("Name: %s\n\n", b);
system("pause");
return 0;
}
The scanf function removes whitespace automatically before trying to parse things other than characters. %c, %n, %[] are exceptions that do not remove leading whitespace.gets is reading the newline left by previous scanf. Catch the newline usinggetchar();
scanf("%d", &a);
getchar(); // catches the newline character omitted by scanf("%d")
gets(b);
https://wpollock.com/CPlus/PrintfRef.htm
Just use 2 gets() functions
When you want to use gets() after a scanf(), you make sure that you use 2 of the gets() functions and for the above case write your code like:
int main(void) {
int a;
char b[20];
printf("Input your ID: ");
scanf("%d", &a);
//the change is here*********************
printf("Input your name: ");
gets(b);
gets(b);
//the change is here*********************
printf("---------");
printf("Name: %s", b);
system("pause");
return 0;
}
#include<stdio.h>
int main() {
char *str, ch;
int count = 0, i;
printf("\nEnter a string : ");
scanf("%s", str);
printf("\nEnter the character to be searched : ");
scanf("%c", &ch);
for (i = 0; str[i] != '\0'; i++) {
if (str[i] == ch)
count++;
}
if (count == 0)
printf("\nCharacter '%c'is not present", ch);
else
printf("\nOccurence of character '%c' : %d", ch, count);
return (0);
}
while i executing this code the string is taken after that it will not taking any characters and showing results.
Your code might crash (happened to me when verifying it on my machine) because you did not allocate space for str...
you should change char *str, ch; to something like char *str = malloc(100), ch;
Also, change scanf("%c", &ch); to scanf(" %c", &ch); to resolve your problem. This happens because when you enter your string, you end it with enter, and that enter is consumed by your next scanf(%c) and so, your second scanf() only reads the enter instead of reading the char you intend. scanf(" %c", &ch); will ignore all whitespaces, including the previously entered enter :-) and wil allow your char to be processed
Always write scanf like this, to read the previous newline character:
printf("\nEnter the character to be searched : ");
scanf(" %c", &ch);
OR
use getchar()
printf("\nEnter the character to be searched : ");
getchar();
scanf("%c", &ch);
Defining a max length would be the simplest way to solve this. Insted of using scanf, I would recomend using fgets as done below. It is much more failsafe since you can define the max number of characters to be read.
Tutorialspoint's explanation of fgets
#define MAX_LENGTH 100
int main() {
char str[MAX_LENGTH], ch;
int count = 0;
printf("\nEnter a string : ");
fgets(str, MAX_LENGTH, stdin);
printf("\nEnter the character to be searched : ");
scanf("%c", &ch);
...
}
I am not too familiar with C syntax. I need to process some data based on user input. Although I processed the data successfully but I am stuck at user input section. I removed the unnecessary data processing section and made a simple example of how I am taking the user input. Can anyone tell me what's the problem with below code :
int i, number;
char *str;
str=(char*)malloc(1000*sizeof(char));
printf("Enter count : ");
scanf("%d", &number);
for(i=0; i<number; i++)
{
printf("\nEnter string: ");
scanf ("%[^\n]%*c", str);
printf("%s", str);
}
Output:
"Enter count : " appears fine, but whenever I provide some value and hit enter it's showing me only 'count' number of Enter string: without enabling user to enter the string.
For example -
Enter count : 2
Enter string:
Enter string:
But if I discard the count input section and provide any fixed value, like
for(i=0; i<5; i++)
it works fine
Thanks in advance
FYI, there is no issue in for(i=0; i<number; i++), problem is in scanning logic.
Actually, scanf ("%[^\n]%*c", str); is not right. you should use %s to read strings, not %c, which reads a single character, including the ENTER (newline).
Rather, i would suggest, use fgets() for inputs. It's a whole lot better in every way. Check the man page here.
Maybe you can use something like
//Dummy code
int i, number;
char *str;
printf("Enter count : ");
scanf("%d", &number);
str=malloc(number*sizeof(char)); //yes, casting not required
fgets(str, (number-1), stdin ); //"number" is used in different context
fputs(str, stdout);
EDIT:
Working code
#include <stdio.h>
#include <stdlib.h>
#define SIZ 1024
int main()
{
int i, number;
char * str = malloc(SIZ * sizeof (char));
printf("Enter the number :\n");
scanf("%d", &number);
getc(stdin); //to eat up the `\n` stored in stdin buffer
for (i = 0; i < number; i++)
{
printf("Enter the string %d :", (i+1));
fgets(str, SIZ-1, stdin);
printf("You have entered :");
fputs(str, stdout);
}
return 0;
}
scanf("%s",str); Use this instead of the code you are using to take string inputs in a character array.
There is a newline character \n after entering count value which is picked up by %c in your scanf()
Just use %s to scan strings as shown below.
scanf("%s",str);
If there are spaces in your input.
Then do
char c[50];
fgets(c,sizeof(c),stdin);
Check the below code:
#include <stdio.h>
#include<stdlib.h>
int main(){
int i, number;
char *str;
str=malloc(1000*sizeof(char));
printf("Enter count : ");
scanf("%d%*c", &number);
for(i=0; i<number; i++)
{
printf("\nEnter string: ");
fgets(str,1000,stdin);
printf("%s", str);
}
}