NAME

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

LIBRARY

       Standard C library (libc, -lc)

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 <= 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 │
       └────────────────────────────────────────────────────────┴───────────────┴────────────────┘

VERSIONS

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

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       C99, POSIX.1-2001, SVr4, 4.3BSD.

       C89 and POSIX.1-1996 include the functions atoi() and atol() only.

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)