Questions tagged [conversion-specifier]
120 questions
65
votes
7 answers
Reading in double values with scanf in c
I try to read-in 2 values using scanf() in C, but the values the system writes into memory are not equal to my entered values. Here is the code:
double a,b;
printf("--------\n"); //seperate lines
scanf("%ld",&a);
printf("--------\n");…
user1880009
- 663
- 1
- 5
- 5
5
votes
3 answers
What is exactly an "invalid conversion specification"?
As per C11, chapter §7.21.6.1, P9
If a conversion specification is invalid, the behavior is undefined.282) If any argument is
not the correct type for the corresponding conversion specification, the behavior is
undefined.
Till time, my…
Sourav Ghosh
- 133,132
- 16
- 183
- 261
4
votes
2 answers
How to separate format specifiers from characters with printf
Another way to phrase this question might be "How to end format specifiers in printf"
If I want to print microseconds in this format 100us using the following code...
long microseconds = 100L;
printf("%lus", microseconds);
only prints 100s because…
baconcheese113
- 843
- 2
- 13
- 27
4
votes
5 answers
How does printing 577 with %c output "A"?
#include
int main()
{
int i = 577;
printf("%c",i);
return 0;
}
After compiling, its giving output "A". Can anyone explain how i'm getting this?
divine ocean
- 59
- 3
4
votes
2 answers
What is the difference between the %PRId and %d format characters?
Consider the following code:
#include
#include
void main(void)
{
int32_t a = 44;
fprintf(stdout, "%d\n", a);
fprintf(stdout, "%"PRId32"\n", a);
}
When is it better to use %d and when would it be better to use…
user7659542
4
votes
2 answers
sscanf(s, "%u", &v) matching signed integers
After Cppcheck was complaining about "%u" as the wrong format specifier to scan into an int variable, I changed the format into "%d", but when having a second look on it before committing the change, I thought that the intention could be to prevent…
Wolf
- 9,679
- 7
- 62
- 108
3
votes
2 answers
Are %f and %lf interchangeable when using printf?
In an article on the w3resource.com, I've seen the following code:
double x, y;
pr1 = sqrt(pr1);
x = (-b + pr1)/(2*a);
y = (-b - pr1)/(2*a);
printf("Root1 = %.5lf\n", x);
printf("Root1 = %.5lf\n", y);
The article says to take three floating-point…
Anik Sen
- 31
- 3
3
votes
2 answers
Why is int to float conversion failing in printf?
When using a int to float implicit conversion, it fails with printf()
#include
int main(int argc, char **argv) {
float s = 10.0;
printf("%f %f %f %f\n", s, 0, s, 0);
return 0;
}
when compiled with gcc -g scale.c -o scale it…
Steve Schnepp
- 4,620
- 5
- 39
- 54
3
votes
2 answers
Is the default value of malloc with the size of a single char P?
char *ptr = malloc(sizeof(char));
printf("\nValue of ptr: %d\n",ptr);
printf("\nValue of address of ptr: %x\n",&ptr);
printf("\nValue of pointed by ptr: %c\n",*ptr);
printf("\nValue of address pointed by ptr: %x\n",&(*ptr));
*ptr='u';
…
NeuronB
- 53
- 6
3
votes
3 answers
Why doesn't the '+' sign work with printf for unsigned values?
I just wrote and ran following program. This just gave an unexpected output without + sign printed to U...MAX.
#include
#include
#include
int main() {
// ...
printf("LLONG_MIN: %+lli\n", LLONG_MIN);
…
Jin Kwon
- 20,295
- 14
- 115
- 184
3
votes
3 answers
sscanf check doesn't work when given more input than required
I have an if statement that is supposed to check if the user entered exactly 4 arguments separated by a var like the following: param1,param2,param3,param4
. Problem is that it doesn't return an error if the user gives more than 4 inputs. It only…
MM1
- 912
- 1
- 10
- 28
3
votes
1 answer
String format in C %*s
I saw somewhere a portion of code in C
char name[51];
int group = 0;
scanf("%*s %50s %*s %d", name, &group);
printf("%s / %d\n", name, group);
If we introduce
"Name:Smith Group:7"
it waits for us to introduce another values. It's strange. What…
user11193267
2
votes
3 answers
Difference between & address and pointer address- Hexadecimal and pointer type data
I am using the following piece of code as a learning exercise for pointers:
int a=8;
int *ptr=&a;
printf("\nThe & address of a is: %x\n",&a);
printf("\nThe value of the pointer ptr is: %p \n",ptr);
I am doing this to identify the address values…
NeuronB
- 53
- 6
2
votes
3 answers
Printf performing implicit casting
In the below code snippet, why do we get an output of 600? Two questions will help me understand the behavior.
I specified the type for variable b to be uint8_t, why doesn't the math operation restrict to the same type?
I thought PRIu8 is the right…
niil87
- 47
- 5
2
votes
5 answers
Getting an integer from a string
I have some code that reads a string of the form name 1 in a while loop, and then I have to extract the integer value to print yes or no. But when I tried to do it with sscanf, it gives the destination integer the value only after the loop…
FlyingDutchMom
- 23
- 3