atoi

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

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

SYNOPSIS
       #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

DESCRIPTION
       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
       The converted value or 0 on error.

ATTRIBUTES
       For an  explanation  of  the  terms  used  in  this  section,  see  at-
       tributes(7).

       +------------------------+---------------+----------------+
       |Interface               | Attribute     | Value          |
       +------------------------+---------------+----------------+
       |atoi(), atol(), atoll() | Thread safety | MT-Safe locale |
       +------------------------+---------------+----------------+
CONFORMING TO
       POSIX.1-2001,  POSIX.1-2008,  C99,  SVr4, 4.3BSD.  C89 and POSIX.1-1996
       include the functions atoi() and atol() only.

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

BUGS
       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  un-
       derflow  are  done.  Only base-10 input can be converted.  It is recom-
       mended to instead use the strtol() and strtoul() family of functions in
       new programs.

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

COLOPHON
       This  page  is  part of release 5.10 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
       https://www.kernel.org/doc/man-pages/.

GNU                               2020-08-13                           ATOI(3)