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.
Name
Synopsis
Description
Return Value
Errors
Examples
Converting an Argument
Application Usage
Rationale
Future Directions
See Also
Copyright
atoi - convert a string to an integer
#include <stdlib.h>
int atoi(const char *str);
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.
The atoi() function shall return the converted value if the value can be represented.
No errors are defined.
The following sections are informative.
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); } ...
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.
None.
None.
strtol() , the Base Definitions volume of IEEE Std 1003.1-2001, <stdlib.h>
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 |