atoq(3) — Linux manual page


ATOI(3)                   Linux Programmer's Manual                  ATOI(3)

NAME         top

       atoi, atol, atoll - convert a string to an integer

SYNOPSIS         top

       #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)):

           _ISOC99_SOURCE ||
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION         top

       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.

RETURN VALUE         top

       The converted value or 0 on error.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface               Attribute     Value          │
       │atoi(), atol(), atoll() │ Thread safety │ MT-Safe locale │

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008, C99, SVr4, 4.3BSD.  C89 and POSIX.1-1996
       include the functions atoi() and atol() only.

NOTES         top

       POSIX.1 leaves the return value of atoi() on error unspecified.  On
       glibc, musl libc, and uClibc, 0 is returned on error.

BUGS         top

       errno is not set on error so there is no way to distinguish between 0
       as an error and as the converted value.  No checks for overflow or
       underflow are done.  Only base-10 input can be converted.  It is
       recommended to instead use the strtol() and strtoul() family of
       functions in new programs.

SEE ALSO         top

       atof(3), strtod(3), strtol(3), strtoul(3)

COLOPHON         top

       This page is part of release 5.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

GNU                              2020-08-13                          ATOI(3)