Free Knowledge Resources


Linux Manual Pages


Free Software * Books

Source Code

Free Media

Linux

strdup(3)


NAME

   strdup, strndup, strdupa, strndupa - duplicate a string

SYNOPSIS

   #include <string.h>

   char *strdup(const char *s);

   char *strndup(const char *s, size_t n);
   char *strdupa(const char *s);
   char *strndupa(const char *s, size_t n);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

   strdup():
       _XOPEN_SOURCE >= 500
           || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
           || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
   strndup():
       Since glibc 2.10:
           _POSIX_C_SOURCE >= 200809L
       Before glibc 2.10:
           _GNU_SOURCE
   strdupa(), strndupa(): _GNU_SOURCE

DESCRIPTION

   The  strdup()  function  returns  a  pointer to a new string which is a
   duplicate of the string s.  Memory for the new string is obtained  with
   malloc(3), and can be freed with free(3).

   The strndup() function is similar, but copies at most n bytes.  If s is
   longer than n, only n bytes are copied, and  a  terminating  null  byte
   ('\0') is added.

   strdupa() and strndupa() are similar, but use alloca(3) to allocate the
   buffer.  They are available only when using  the  GNU  GCC  suite,  and
   suffer from the same limitations described in alloca(3).

RETURN VALUE

   On  success,  the strdup() function returns a pointer to the duplicated
   string.  It returns NULL if insufficient  memory  was  available,  with
   errno set to indicate the cause of the error.

ERRORS

   ENOMEM Insufficient memory available to allocate duplicate string.

ATTRIBUTES

   For   an   explanation   of   the  terms  used  in  this  section,  see
   attributes(7).

   
   Interface                        Attribute      Value   
   
   strdup(), strndup(), strdupa(),  Thread safety  MT-Safe 
   strndupa()

CONFORMING TO

   strdup() conforms to SVr4, 4.3BSD, POSIX.1-2001.  strndup() conforms to
   POSIX.1-2008.  strdupa() and strndupa() are GNU extensions.

SEE ALSO

   alloca(3),   calloc(3),   free(3),  malloc(3),  realloc(3),  string(3),
   wcsdup(3)

COLOPHON

   This page is part of release 4.09 of the Linux  man-pages  project.   A
   description  of  the project, information about reporting bugs, and the
   latest    version    of    this    page,    can     be     found     at
   https://www.kernel.org/doc/man-pages/.



Opportunity


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.



Free Software


Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.



Free Books


The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.



Education


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.


birds banner