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
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 (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 at-
tributes(7).
┌────────────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├────────────────────────────────────────────┼───────────────┼─────────┤
│envz_add(), envz_entry(), envz_get(), │ Thread safety │ MT-Safe │
│envz_merge(), envz_remove(), envz_strip() │ │ │
└────────────────────────────────────────────┴───────────────┴─────────┘
STANDARDS
These functions are a GNU extension.
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 6.03 2023-02-05 envz_add(3)
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