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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 **restrict envz, size_t *restrict envz_len,
                      const char *restrict name, const char *restrict value);

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

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

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

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

       void envz_strip(char **restrict envz, size_t *restrict 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 (an integer type), 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(), envz_get(), envz_merge(), envz_remove(), envz_strip()                                                       │ Thread safety │ MT-Safe │
       └──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

CONFORMING TO
       These functions are a GNU extension.

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

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

           for (int 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)

                                                                               2021-03-22                                                                    ENVZ_ADD(3)