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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 .