This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

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

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group  Base
       Specifications  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  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.opengroup.org/unix/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                                   2017                                          ATOI(3POSIX)

       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.1‐2017 defers to the ISO C standard.

       The call atoi(str) shall be equivalent to:

           (int) strtol(str, (char **)NULL, 10)

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

       No errors are defined.

       Thefollowingsectionsareinformative.

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

           #include <stdlib.h>
           #include <stdio.h>
           ...
           int minutes_to_event;
           ...
           if (argc < 2 || ((minutes_to_event = atoi (argv[1]))) <= 0) {
              fprintf(stderr, "Usage: %s minutes\n", argv[0]); exit(1);
           }
           ...

       None.

       atoi — convert a string to an integer

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

       None.

       The atoi() function shall return the converted value if the value can be represented.

strtol()

       The Base Definitions volume of POSIX.1‐2017, <stdlib.h>

       #include <stdlib.h>

       int atoi(const char *str);