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ENVZ_ADD(3)                Linux Programmer's Manual               ENVZ_ADD(3)
NAME
       envz_add,  envz_entry,  envz_get, envz_merge, envz_remove, envz_strip -
       environment string support
SYNOPSIS
       #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);
DESCRIPTION
       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.
RETURN VALUE
       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
       occurs.
ATTRIBUTES
       For  an  explanation  of  the  terms  used   in   this   section,   see
       attributes(7).
       +----------------------------+---------------+---------+
       |Interface                   | Attribute     | Value   |
       +----------------------------+---------------+---------+
       |envz_add(), envz_entry(),   | Thread safety | MT-Safe |
       |envz_get(), envz_merge(),   |               |         |
       |envz_remove(), envz_strip() |               |         |
       +----------------------------+---------------+---------+
CONFORMING TO
       These functions are a GNU extension.  Handle with care.
EXAMPLE
       #include <stdio.h>
       #include <stdlib.h>
       #include <envz.h>
       int
       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);
           exit(EXIT_SUCCESS);
       }
SEE ALSO
       argz_add(3)
COLOPHON
       This  page  is  part of release 4.15 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/.
                                  2017-09-15                       ENVZ_ADD(3)