envz_add(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | CONFORMING TO | EXAMPLES | SEE ALSO | COLOPHON

ENVZ_ADD(3)             Linux Programmer's Manual            ENVZ_ADD(3)

NAME         top

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

SYNOPSIS         top

       #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         top

       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         top

       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         top

       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         top

       These functions are a GNU extension.

EXAMPLES         top

       #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         top

       argz_add(3)

COLOPHON         top

       This page is part of release 5.10 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/.

                               2020-11-01                    ENVZ_ADD(3)

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