mirror of https://github.com/mkerrisk/man-pages
155 lines
3.7 KiB
Groff
155 lines
3.7 KiB
Groff
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.\" References consulted:
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.\" Linux libc source code
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.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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.\" 386BSD man pages
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.\" Modified Sun Jul 25 10:41:34 1993 by Rik Faith (faith@cs.unc.edu)
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.\" Modified Wed Oct 17 01:12:26 2001 by John Levon <moz@compsoc.man.ac.uk>
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.TH STRDUP 3 2019-03-06 "GNU" "Linux Programmer's Manual"
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.SH NAME
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strdup, strndup, strdupa, strndupa \- duplicate a string
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.SH SYNOPSIS
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.nf
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.B #include <string.h>
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.PP
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.BI "char *strdup(const char *" s );
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.PP
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.BI "char *strndup(const char *" s ", size_t " n );
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.BI "char *strdupa(const char *" s );
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.BI "char *strndupa(const char *" s ", size_t " n );
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.fi
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.PP
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.RS -4
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.RE
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.PP
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.BR strdup ():
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.nf
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_XOPEN_SOURCE >= 500
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.\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
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|| /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
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|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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.fi
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.PP
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.BR strndup ():
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.nf
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Since glibc 2.10:
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_POSIX_C_SOURCE >= 200809L
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Before glibc 2.10:
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_GNU_SOURCE
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.fi
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.PP
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.BR strdupa (),
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.BR strndupa ():
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.nf
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_GNU_SOURCE
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.fi
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.SH DESCRIPTION
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The
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.BR strdup ()
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function returns a pointer to a new string which
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is a duplicate of the string
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.IR s .
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Memory for the new string is
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obtained with
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.BR malloc (3),
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and can be freed with
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.BR free (3).
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.PP
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The
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.BR strndup ()
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function is similar, but copies at most
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.I n
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bytes.
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If
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.I s
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is longer than
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.IR n ,
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only
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.I n
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bytes are copied, and a terminating null byte (\(aq\e0\(aq) is added.
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.PP
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.BR strdupa ()
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and
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.BR strndupa ()
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are similar, but use
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.BR alloca (3)
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to allocate the buffer.
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They are available only when using the GNU
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GCC suite, and suffer from the same limitations described in
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.BR alloca (3).
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.SH RETURN VALUE
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On success, the
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.BR strdup ()
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function returns a pointer to the duplicated
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string.
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It returns NULL if insufficient memory was available, with
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.I errno
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set to indicate the error.
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.SH ERRORS
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.TP
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.B ENOMEM
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Insufficient memory available to allocate duplicate string.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.ad l
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.nh
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.TS
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allbox;
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lbx lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR strdup (),
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.BR strndup (),
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.BR strdupa (),
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.BR strndupa ()
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T} Thread safety MT-Safe
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.TE
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.hy
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.ad
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.sp 1
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.SH CONFORMING TO
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.\" 4.3BSD-Reno, not (first) 4.3BSD.
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.BR strdup ()
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conforms to SVr4, 4.3BSD, POSIX.1-2001.
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.BR strndup ()
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conforms to POSIX.1-2008.
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.BR strdupa ()
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and
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.BR strndupa ()
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are GNU extensions.
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.SH SEE ALSO
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.BR alloca (3),
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.BR calloc (3),
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.BR free (3),
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.BR malloc (3),
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.BR realloc (3),
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.BR string (3),
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.BR wcsdup (3)
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