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NAME

   atoi - convert a string to an integer

SYNOPSIS

   #include <stdlib.h>

   int atoi(const char *str);

DESCRIPTION

   [CX] [Option Start] 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 defers to the ISO C standard. [Option End]

   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.

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.