atoi, atol, atoll - convert a string to an integer
#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
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
.
The converted value or 0 on error.
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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