NAME
atoi — convert a
string to an integer
SYNOPSIS
#include
<stdlib.h>
int atoi(const char *str);
DESCRIPTION
[CX] 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 IEEE Std 1003.1-2001 (“POSIX.1”) 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.
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(3) but is retained because it is used extensively
in existing code. If the number is not known to be in range,
strtol(3) should be used because
atoi () is not required to perform any error
checking.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
strtol(3), the Base Definitions volume of IEEE Std 1003.1-2001 (“POSIX.1”), <stdlib.h>
CHANGE HISTORY
First released in Issue 1. Derived from Issue 1 of the SVID.
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