1ATOI(3P)                   POSIX Programmer's Manual                  ATOI(3P)
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PROLOG

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

13       atoi — convert a string to an integer
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SYNOPSIS

16       #include <stdlib.h>
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18       int atoi(const char *str);
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DESCRIPTION

21       The functionality described on this reference page is aligned with  the
22       ISO C  standard.  Any  conflict between the requirements described here
23       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2008
24       defers to the ISO C standard.
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26       The call atoi(str) shall be equivalent to:
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28           (int) strtol(str, (char **)NULL, 10)
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30       except  that  the handling of errors may differ. If the value cannot be
31       represented, the behavior is undefined.
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RETURN VALUE

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

38       No errors are defined.
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40       The following sections are informative.
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EXAMPLES

43   Converting an Argument
44       The  following example checks for proper usage of the program. If there
45       is an argument and the decimal conversion of  this  argument  (obtained
46       using atoi()) is greater than 0, then the program has a valid number of
47       minutes to wait for an event.
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49           #include <stdlib.h>
50           #include <stdio.h>
51           ...
52           int minutes_to_event;
53           ...
54           if (argc < 2 || ((minutes_to_event = atoi (argv[1]))) <= 0) {
55              fprintf(stderr, "Usage: %s minutes\n", argv[0]); exit(1);
56           }
57           ...
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APPLICATION USAGE

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

66       None.
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FUTURE DIRECTIONS

69       None.
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SEE ALSO

72       strtol()
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74       The Base Definitions volume of POSIX.1‐2008, <stdlib.h>
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77       Portions  of  this text are reprinted and reproduced in electronic form
78       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
79       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
80       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
81       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
82       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  In  the
83       event of any discrepancy between this version and the original IEEE and
84       The Open Group Standard, the original IEEE and The Open Group  Standard
85       is  the  referee document. The original Standard can be obtained online
86       at http://www.unix.org/online.html .
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88       Any typographical or formatting errors that appear  in  this  page  are
89       most likely to have been introduced during the conversion of the source
90       files to man page format. To report such errors,  see  https://www.ker‐
91       nel.org/doc/man-pages/reporting_bugs.html .
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95IEEE/The Open Group                  2013                             ATOI(3P)
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