envz_add,  envz_entry,  envz_get, envz_merge, envz_remove, envz_strip -
   environment string support


   #include <envz.h>

   error_t envz_add(char **envz, size_t *envz_len,
                    const char *name, const char *value);

   char *envz_entry(const char *envz, size_t envz_len, const char *name);

   char *envz_get(const char *envz, size_t envz_len, const char *name);

   error_t envz_merge(char **envz, size_t *envz_len,
                      const char *envz2, size_t envz2_len, int override);

   void envz_remove(char **envz, size_t *envz_len, const char *name);

   void envz_strip(char **envz, size_t *envz_len);


   These functions are glibc-specific.

   An argz vector is a pointer to  a  character  buffer  together  with  a
   length,  see  argz_add(3).   An  envz  vector is a special argz vector,
   namely one where the strings have the  form  "name=value".   Everything
   after the first '=' is considered to be the value.  If there is no '=',
   the value is taken to be NULL.  (While the value in case of a  trailing
   '=' is the empty string "".)

   These functions are for handling envz vectors.

   envz_add()  adds the string "name=value" (in case value is non-NULL) or
   "name" (in case value is NULL) to the  envz  vector  (*envz, *envz_len)
   and  updates  *envz  and  *envz_len.   If  an  entry with the same name
   existed, it is removed.

   envz_entry() looks for name in the  envz  vector  (envz, envz_len)  and
   returns the entry if found, or NULL if not.

   envz_get()  looks  for  name  in  the  envz vector (envz, envz_len) and
   returns the value if found, or NULL if not.  (Note that the  value  can
   also be NULL, namely when there is an entry for name without '=' sign.)

   envz_merge()  adds each entry in envz2 to *envz, as if with envz_add().
   If override is true, then values in envz2 will supersede those with the
   same name in *envz, otherwise not.

   envz_remove()  removes  the  entry  for name from (*envz, *envz_len) if
   there was one.

   envz_strip() removes all entries with value NULL.


   All envz functions that do memory allocation  have  a  return  type  of
   error_t,  and  return  0 for success, and ENOMEM if an allocation error


   For  an  explanation  of  the  terms  used   in   this   section,   see

   Interface                    Attribute      Value   
   envz_add(), envz_entry(),    Thread safety  MT-Safe 
   envz_get(), envz_merge(),                           
   envz_remove(), envz_strip()                         


   These functions are a GNU extension.  Handle with care.


   #include <stdio.h>
   #include <stdlib.h>
   #include <envz.h>

   main(int argc, char *argv[], char *envp[])
       int i, e_len = 0;
       char *str;

       for (i = 0; envp[i] != NULL; i++)
           e_len += strlen(envp[i]) + 1;

       str = envz_entry(*envp, e_len, "HOME");
       printf("%s\n", str);
       str = envz_get(*envp, e_len, "HOME");
       printf("%s\n", str);




   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

                              2015-03-02                       ENVZ_ADD(3)


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.


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.