envz_add(3) - Man pages

envz_add(3)                 Library Functions Manual                envz_add(3)

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

LIBRARY
       Standard C library (libc, -lc)

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 af-
       ter 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 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  (an integer type), and return 0 for success, and ENOMEM if an al-
       location 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(),      │ Thread safety │ MT-Safe │
       │ envz_merge(), envz_remove(), envz_strip()  │               │         │
       └────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS
       GNU.

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

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

           for (size_t 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)

Linux man-pages 6.9.1              2024-06-15                       envz_add(3)

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