atoi - convert a string
to an int
atoi, atol, atoll - convert a string to an integer
#include <stdlib.h>
int atoi(string s);
#include <stdlib.h>
int atoi(const char *nptr);
long atol(const char *nptr);
long long atoll(const char *nptr);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
atoll():
_ISOC99_SOURCE || || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
This function converts a (positive or negative) integer from a string
(e.g., "50"
) to an int
(e.g., 50
).
The atoi() function converts the initial portion of the string pointed to by nptr
to int
. The behavior is the same as
strtol(nptr, NULL, 10);
except that atoi() does not detect errors.
The atol() and atoll() functions behave the same as atoi(), except that they convert the initial portion of the string to their return type of long
or long long
.
This function returns its input, s
, as an int
.
The converted value or 0 on error.
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
printf("This is CS%i\n", atoi("50"));
}
For an explanation of the terms used in this section, see attributes(7).
Interface | Attribute | Value |
atoi(), atol(), atoll() | Thread safety | MT-Safe locale |
POSIX.1 leaves the return value of atoi() on error unspecified. On glibc, musl libc, and uClibc, 0 is returned on error.
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