atoi(3)                                               Library Functions Manual                                              atoi(3)

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 │
       └──────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴────────────────┘

STANDARDS
       POSIX.1-2001, POSIX.1-2008, C99, SVr4, 4.3BSD.

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)

Linux man-pages 6.03                                         2023-02-05                                                     atoi(3)