man atoi () - convert a string to an integer

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 .