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



PPRROOLLOOGG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.


NNAAMMEE
       atoi -- convert a string to an integer

SSYYNNOOPPSSIISS
       #include <stdlib.h>

       int atoi(const char *_s_t_r);

DDEESSCCRRIIPPTTIIOONN
       The functionality described on this reference page is aligned with the
       ISO C standard. Any conflict between the requirements described here
       and the ISO C standard is unintentional. This volume of POSIX.1-2008
       defers to the ISO C standard.

       The call _a_t_o_i(_s_t_r) shall be equivalent to:

           ((iinntt)) ssttrrttooll((ssttrr,, ((cchhaarr ****))NNUULLLL,, 1100))

       except that the handling of errors may differ. If the value cannot be
       represented, the behavior is undefined.

RREETTUURRNN VVAALLUUEE
       The _a_t_o_i() function shall return the converted value if the value can
       be represented.

EERRRROORRSS
       No errors are defined.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
   CCoonnvveerrttiinngg aann AArrgguummeenntt
       The following example checks for proper usage of the program. If there
       is an argument and the decimal conversion of this argument (obtained
       using _a_t_o_i()) is greater than 0, then the program has a valid number of
       minutes to wait for an event.

           ##iinncclluuddee <<ssttddlliibb..hh>>
           ##iinncclluuddee <<ssttddiioo..hh>>
           ......
           iinntt mmiinnuutteess__ttoo__eevveenntt;;
           ......
           iiff ((aarrggcc << 22 |||| ((((mmiinnuutteess__ttoo__eevveenntt == aattooii ((aarrggvv[[11]])))))) <<== 00)) {{
              ffpprriinnttff((ssttddeerrrr,, ""UUssaaggee:: %%ss mmiinnuutteess\\nn"",, aarrggvv[[00]]));; eexxiitt((11));;
           }}
           ......

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       The _a_t_o_i() function is subsumed by _s_t_r_t_o_l() but is retained because it
       is used extensively in existing code. If the number is not known to be
       in range, _s_t_r_t_o_l() should be used because _a_t_o_i() is not required to
       perform any error checking.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _s_t_r_t_o_l()

       The Base Definitions volume of POSIX.1-2008, <<ssttddlliibb..hh>>

CCOOPPYYRRIIGGHHTT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be obtained online
       at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2013                              ATOI(3)
