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

COLOPHON
       This page is part of release 5.09 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)