ATOI(3) Linux Programmer's Manual ATOI(3)
atoi, atol, atoll, atoq - convert a string to an integer
int atoi(const char *nptr);
long atol(const char *nptr);
long long atoll(const char *nptr);
long long atoq(const char *nptr);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
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. atoq() is an
obsolete name for atoll().
The converted value.
Multithreading (see pthreads(7))
The atoi(), atol(), and atoll() functions are thread-safe with exceptions. These func-
tions can be safely used in multithreaded applications, as long as setlocale(3) is not
called to change the locale.
SVr4, POSIX.1-2001, 4.3BSD, C99. C89 and POSIX.1-1996 include the functions atoi() and
atol() only. atoq() is a GNU extension.
The nonstandard atoq() function is not present in libc 4.6.27 or glibc 2, but is present
in libc5 and libc 4.7 (though only as an inline function in <stdlib.h> until libc 5.4.44).
The atoll() function is present in glibc 2 since version 2.0.2, but not in libc4 or libc5.
atof(3), strtod(3), strtol(3), strtoul(3)
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GNU 2013-10-14 ATOI(3)