I want to process user input as an integer, but it seems as though C has no way to get an int from stdin. Is there a function to do this? How would I go about getting an int from the user?
+6
A:
#include <stdio.h>
int n;
scanf ("%d",&n);
See http://www.cplusplus.com/reference/clibrary/cstdio/scanf/
Marc W
2009-05-14 19:44:32
A:
#include <stdio.h>
main() {
int i = 0;
int k,j=10;
i=scanf("%d%d%d",&j,&k,&i);
printf("total values inputted %d\n",i);
printf("The input values %d %d\n",j,k);
}
from here
Konstantinos
2009-05-14 19:45:16
This looks very suspicious, it both stores the result of scanf() in i, and reads a value into i at the same time. Not recommendable.
unwind
2009-05-14 20:10:06
+1
A:
The standard library function scanf is used for formatted input: %d int (the d is short for decimal)
#include <stdio.h>
int main(void)
{
int number;
printf("Enter a number from 1 to 1000: ");
scanf("%d",&number);
printf("Your number is %d\n",number);
return 0;
}
TStamper
2009-05-14 19:48:04
+4
A:
scanf()
is the answer, but you should certainly check the return value since many, many things can go wrong parsing numbers from external input...
int num, nitems;
nitems = scanf("%d", &num);
if (nitems == EOF) {
/* Handle EOF/Failure */
} else if (nitems == 0) {
/* Handle no match */
} else {
printf("Got %d\n", num);
}
dwc
2009-05-14 20:01:59
+1
A:
Aside from (f)scanf
, which has been sufficiently discussed by the other answers, there is also atoi
and strtol
, for cases when you already have read input into a string but want to convert it into an int
or long
.
char *line;
scanf("%s", line);
int i = atoi(line); /* Array of chars TO Integer */
long l = strtol(line, NULL, 10); /* STRing (base 10) TO Long */
/* base can be between 2 and 36 inclusive */
strtol
is recommended because it allows you to determine whether a number was successfully read or not (as opposed to atoi
, which has no way to report any error, and will simply return 0 if it given garbage).
char *strs[] = {"not a number", "10 and stuff", "42"};
int i;
for (i = 0; i < sizeof(strs) / sizeof(*strs); i++) {
char *end;
long l = strtol(strs[i], &end, 10);
if (end == line)
printf("wasn't a number\n");
else if (end[0] != '\0')
printf("trailing characters after number %l: %s\n", l, end);
else
printf("happy, exact parse of %l\n", l);
}
ephemient
2009-05-14 20:57:46