Manual Reference Pages  - ATOI (P)

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.

CONTENTS

Name
Synopsis
Description
Return Value
Errors
Examples
     Converting an Argument
Application Usage
Rationale
Future Directions
See Also
Copyright

NAME

atoi - convert a string to an integer

SYNOPSIS

#include <stdlib.h>

int atoi(const char *str);

DESCRIPTION

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 IEEE Std 1003.1-2001, <stdlib.h>

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 .


IEEE/The Open Group ATOI (P) 2003
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