PROLOG

       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.

NAME

       atoi — convert a string to an integer

SYNOPSIS

       #include <stdlib.h>

       int atoi(const char *str);

DESCRIPTION

       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.

RETURN VALUE

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

ERRORS

       No errors are defined.

       The following sections are informative.

EXAMPLES

   Converting an Argument
       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);
           }
           ...

APPLICATION USAGE

       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.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       strtol()

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

COPYRIGHT

       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 .