ATOI(3) | Library Functions Manual | ATOI(3)

# NAME

`atoi` — convert ASCII string to integer

# SYNOPSIS

`#include <stdlib.h>`

int
`atoi`(const char *nptr);

# DESCRIPTION

The `atoi`() function converts the initial portion of the string pointed to by nptr to integer representation.

It is equivalent to:

    (int)strtol(nptr, (char **)NULL, 10);

# SEE ALSO

atof(3), atol(3), strtod(3), strtol(3), strtonum(3), strtoul(3)

# STANDARDS

The `atoi`() function conforms to ANSI X3.159-1989 (“ANSI C89”).

# HISTORY

An `atoi`() function first appeared in Version 1 AT&T UNIX.

# CAVEATS

`atoi` does no overflow checking, handles unsigned numbers poorly, and handles strings containing trailing extra characters (like “123abc”) poorly. Careful use of strtol(3) and strtoul(3) can alleviate these problems, but strtonum(3) can be used to convert numbers from strings much more safely and easily.

September 11, 2022 | Debian