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 |
       +-------------------------------------+---------------+----------------+
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)

Linux man-pages 6.7               2023-10-31                           atoi(3)