ENVZ_ADD(3)

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 ex-
       isted, it is removed.

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

       envz_get()  looks  for name in the envz vector (envz, envz_len) and re-
       turns 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  er-
       ror_t,  and return 0 for success, and ENOMEM if an allocation error oc-
       curs.

ATTRIBUTES
       For an  explanation  of  the  terms  used  in  this  section,  see  at-
       tributes(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.

EXAMPLES
       #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 5.07 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/.

                                  2020-06-09                       ENVZ_ADD(3)