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When running the program and entering the text, it will ask me again and again to insert the input, until I give an input of one character only.
NOTE: it isn't in any sort of cycle loop, I don't know what the problem is. (I'm using cs50 library for the get char).
char nameless[] = { get_char("Insert the text here: ")};
char nameless[] = {get_char("Insert the text here: ")};
If you look up get_char(), it clearly states
Prompts user for a line of text from standard input and returns the equivalent char; if text does not represent a single char, user is reprompted.
You need to enter only one character. Not a line of characters or 'text' as you call it.
Enter char: a
That's it.
Here's a working code example:
#include <cs50.h>
int main(void)
{
// attempt to read character from stdin
char c = get_char("Enter char: ");
// ensure character was read successfully
if (c == CHAR_MAX)
{
return 1;
}
char next = get_char("You just entered %c. Enter another char: ", c);
if (next == CHAR_MAX)
{
return 1;
}
printf("The last char you entered was %c\n", next);
}
You can look it up at CS50 Library for C
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#include <stdio.h>
#include <string.h>
struct student_details{
char name[34];
int roll;
char section;
};
int main(){
struct student_details student[5];
for (int i = 0; i < 5; i++)
{
printf("Your full name = ");
scanf("%s", student[i].name);
printf("Your roll = ");
scanf("%d", student[i].roll);
}
return 0;
}
I think something is wrong with my code anyone please fix this.
When I run this code, it's Shows an error. after running this code this code take 1 time input and second input is skipped.
The scanf function expects to accept a format string and then pointers to the data you want to scan into. student[i].name is an array, which in this case decays into a pointer to its first element. This works.
Note: This array only contains 34 characters. With the null terminator, you want to use a width specifier with scanf to limit the input and prevent a buffer overflow. "%33s"
When you try to read the roll:
scanf("%d", student[i].roll);
student[i].roll is an int, not a pointer. But pointers are numbers, so this will compile. Your compiler should warn you about it, though. But, then the program tries to dereference this value it thinks is a pointer, and a segmentation fault occurs.
What you want to do is pass the address of student[i].roll.
scanf("%d", &student[i].roll);
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#include<stdio.h>
int main()
{
char word[1000];
scanf("word%s", word);
printf("%s", word);
}
It seems that when I input any string, as long as I type out "word" first, I get proper output.
But is this program actually valid
It compiles and therefore is valid from a syntax perspective. It's also fine in order to check that a prefix is used.
However, there are at least two ways to get undefined behaviour:
scanf might store more than 1000 characters (read 999 and one for the final \0)
scanf might read none if the input does not start with "word"
You should therefore check the result of scanf, initialize word, and also limit the maximum number of characters that scanf reads:
#include<stdio.h>
int main()
{
char word[1000] = {0};
int ret = scanf("word%999s", word);
if ( ret == 1 ) {
printf("%s", word);
}
}
this program is valid ,but you have to be careful about buffer overflow , which means if user input more than 999 chars this will lead to undefined behavior , so I suggest this:
scanf("word%999s", word);
also as you said as long as I type out "word" first ,otherwise char word[1000] will be uninitialized.
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The first ScanF takes both inputs when I type a character and an integer is expected.
see image below:
As you can see when I type "55ape" for ScanNum_A it sets ScanNum_B = 0.
Why does this happen?
It happens because
ape is still left in the input stream and your second scanf tries to read it but fails as it was expecting integer but found chars.
You can clear the input buffer after your first scanf as below.
//first scanf
int c;
while ((c = getchar()) != '\n' && c != EOF) { }
//second scanf
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So im making a program that checks if a word is a palindrome but when it comes to comparing the final strings at the end even if they are the same i get a -1 result edit: copy pasted the exact same code i used
#include<stdlib.h>
#include<stdio.h>
#include<string.h>
int main()
{
char input[50];
char test[50];
int ret;
printf("Enter word or phrase to compare ");
fgets(input,sizeof(input),stdin);
strcpy(test,input);
strrev(input);
ret = strcmp(test,input);
if(ret == 0)
printf("\n this is a palindrome ");
else
printf("\n this is not a palindrome");
}
For input i used "ala" which i know is a palindrome i get the result
this is not a palindrome
Demonstration on IDEONE.
The problem is that you call strrev without stripping off the newline from your input obtained from fgets. This causes your reversed string to have the newline at the beginning of the string, which would cause a mismatch even if you intended to provide a palindrome as the input.
While there are various ways to achieve this, one way would be to look at the last byte of your input, and see if it is a newline character. If it is, remove it.
if (fgets(input,sizeof(input),stdin) == NULL) {
/* todo: ... handle error ... */
return 0;
}
len = strlen(input);
if (input[len-1] == '\n') input[--len] = '\0';
strcpy(test,input);
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I have this structure after scanning and printing p and q are printed while r is not printed can you please let me know why?
struct book
{
int p;
float q;
char r;
};
int main()
{
struct book b;
scanf("%d%f",&b.p,&b.q);
scanf("%c",&b.r);
printf("%d......%f.....%c",b.p,b.q,b.r);
return 0;
}
Problem :
that's because b.r takes in the \n character entered at the end of the previous scanf() statement
scanf("%d%f",&b.p,&b.q);
Solution :
Avoid it by giving a space before %c in the scanf()
scanf(" %c",&b.r);
Why give a space ?
This would consume if there are any whitespaces (' ' or '\n' or '\0') present in the input stream
Suggestion :
next time when you don't get any output when you print, try printing it's ascii value by casting it to int, that way you'd know what value the variable is taking and see it's corresponding character in ascii table.
printf("%d",(int) b.r);
for example, without making any changes to your code except this to your printf statement :
printf("%d......%f.....%d",b.p,b.q,(int)b.r);
you'd get
input :
2
2
output :
2.....2.....10
why the 10?
because it's the ascii value of \n or the newline character