atoi

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



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 .



IEEE/The Open Group                   2017                              ATOI(3P)