| .\" 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 |
| .\" preserved on all copies. |
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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| .\" manual page may be incorrect or out-of-date.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 Sun Jul 25 10:41:34 1993 by Rik Faith (faith@cs.unc.edu) |
| .\" Modified Wed Oct 17 01:12:26 2001 by John Levon <moz@compsoc.man.ac.uk> |
| .TH STRDUP 3 2021-03-22 "GNU" "Linux Programmer's Manual" |
| .SH NAME |
| strdup, strndup, strdupa, strndupa \- duplicate a string |
| .SH SYNOPSIS |
| .nf |
| .B #include <string.h> |
| .PP |
| .BI "char *strdup(const char *" s ); |
| .PP |
| .BI "char *strndup(const char *" s ", size_t " n ); |
| .BI "char *strdupa(const char *" s ); |
| .BI "char *strndupa(const char *" s ", size_t " n ); |
| .fi |
| .PP |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| .BR strdup (): |
| .nf |
| _XOPEN_SOURCE >= 500 |
| .\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED |
| || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L |
| || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE |
| .fi |
| .PP |
| .BR strndup (): |
| .nf |
| Since glibc 2.10: |
| _POSIX_C_SOURCE >= 200809L |
| Before glibc 2.10: |
| _GNU_SOURCE |
| .fi |
| .PP |
| .BR strdupa (), |
| .BR strndupa (): |
| .nf |
| _GNU_SOURCE |
| .fi |
| .SH DESCRIPTION |
| The |
| .BR strdup () |
| function returns a pointer to a new string which |
| is a duplicate of the string |
| .IR s . |
| Memory for the new string is |
| obtained with |
| .BR malloc (3), |
| and can be freed with |
| .BR free (3). |
| .PP |
| The |
| .BR strndup () |
| function is similar, but copies at most |
| .I n |
| bytes. |
| If |
| .I s |
| is longer than |
| .IR n , |
| only |
| .I n |
| bytes are copied, and a terminating null byte (\(aq\e0\(aq) is added. |
| .PP |
| .BR strdupa () |
| and |
| .BR strndupa () |
| are similar, but use |
| .BR alloca (3) |
| to allocate the buffer. |
| They are available only when using the GNU |
| GCC suite, and suffer from the same limitations described in |
| .BR alloca (3). |
| .SH RETURN VALUE |
| On success, the |
| .BR strdup () |
| function returns a pointer to the duplicated |
| string. |
| It returns NULL if insufficient memory was available, with |
| .I errno |
| set to indicate the error. |
| .SH ERRORS |
| .TP |
| .B ENOMEM |
| Insufficient memory available to allocate duplicate string. |
| .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 strdup (), |
| .BR strndup (), |
| .BR strdupa (), |
| .BR strndupa () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| .\" 4.3BSD-Reno, not (first) 4.3BSD. |
| .BR strdup () |
| conforms to SVr4, 4.3BSD, POSIX.1-2001. |
| .BR strndup () |
| conforms to POSIX.1-2008. |
| .BR strdupa () |
| and |
| .BR strndupa () |
| are GNU extensions. |
| .SH SEE ALSO |
| .BR alloca (3), |
| .BR calloc (3), |
| .BR free (3), |
| .BR malloc (3), |
| .BR realloc (3), |
| .BR string (3), |
| .BR wcsdup (3) |