| .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) |
| .\" |
| .\" %%%LICENSE_START(VERBATIM) |
| .\" Permission is granted to make and distribute verbatim copies of this |
| .\" manual provided the copyright notice and this permission notice are |
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| .\" |
| .\" Permission is granted to copy and distribute modified versions of this |
| .\" manual under the conditions for verbatim copying, provided that the |
| .\" entire resulting derived work is distributed under the terms of a |
| .\" permission notice identical to this one. |
| .\" |
| .\" Since the Linux kernel and libraries are constantly changing, this |
| .\" manual page may be incorrect or out-of-date. The author(s) assume no |
| .\" responsibility for errors or omissions, or for damages resulting from |
| .\" the use of the information contained herein. The author(s) may not |
| .\" have taken the same level of care in the production of this manual, |
| .\" which is licensed free of charge, as they might when working |
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| .\" Formatted or processed versions of this manual, if unaccompanied by |
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| .\" %%%LICENSE_END |
| .\" |
| .\" References consulted: |
| .\" Linux libc source code |
| .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) |
| .\" 386BSD man pages |
| .\" Modified Mon Mar 29 22:39:41 1993, David Metcalfe |
| .\" Modified Sat Jul 24 21:38:42 1993, Rik Faith (faith@cs.unc.edu) |
| .\" Modified Sun Dec 17 18:35:06 2000, Joseph S. Myers |
| .\" |
| .TH ATOI 3 2021-03-22 "GNU" "Linux Programmer's Manual" |
| .SH NAME |
| atoi, atol, atoll \- convert a string to an integer |
| .SH SYNOPSIS |
| .nf |
| .B #include <stdlib.h> |
| .PP |
| .BI "int atoi(const char *" nptr ); |
| .BI "long atol(const char *" nptr ); |
| .BI "long long atoll(const char *" nptr ); |
| .fi |
| .PP |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| .BR atoll (): |
| .nf |
| _ISOC99_SOURCE |
| || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE |
| .fi |
| .SH DESCRIPTION |
| The |
| .BR atoi () |
| function converts the initial portion of the string |
| pointed to by \fInptr\fP to |
| .IR int . |
| The behavior is the same as |
| .PP |
| .in +4n |
| .EX |
| strtol(nptr, NULL, 10); |
| .EE |
| .in |
| .PP |
| except that |
| .BR atoi () |
| does not detect errors. |
| .PP |
| The |
| .BR atol () |
| and |
| .BR atoll () |
| functions behave the same as |
| .BR atoi (), |
| except that they convert the initial portion of the |
| string to their return type of \fIlong\fP or \fIlong long\fP. |
| .SH RETURN VALUE |
| The converted value or 0 on error. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR atoi (), |
| .BR atol (), |
| .BR atoll () |
| T} Thread safety MT-Safe locale |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| POSIX.1-2001, POSIX.1-2008, C99, SVr4, 4.3BSD. |
| C89 and |
| POSIX.1-1996 include the functions |
| .BR atoi () |
| and |
| .BR atol () |
| only. |
| .\" .SH NOTES |
| .\" Linux libc provided |
| .\" .BR atoq () |
| .\" as an obsolete name for |
| .\" .BR atoll (); |
| .\" .BR atoq () |
| .\" is not provided by glibc. |
| .\" The |
| .\" .BR atoll () |
| .\" function is present in glibc 2 since version 2.0.2, but |
| .\" not in libc4 or libc5. |
| .SH NOTES |
| POSIX.1 leaves the return value of |
| .BR atoi () |
| on error unspecified. |
| On glibc, musl libc, and uClibc, 0 is returned on error. |
| .SH BUGS |
| .I errno |
| is not set on error so there is no way to distinguish between 0 as an |
| error and as the converted value. |
| No checks for overflow or underflow are done. |
| Only base-10 input can be converted. |
| It is recommended to instead use the |
| .BR strtol () |
| and |
| .BR strtoul () |
| family of functions in new programs. |
| .SH SEE ALSO |
| .BR atof (3), |
| .BR strtod (3), |
| .BR strtol (3), |
| .BR strtoul (3) |