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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | STANDARDS | EXAMPLES | SEE ALSO | COLOPHON |
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envz_add(3) Library Functions Manual envz_add(3)
envz_add, envz_entry, envz_get, envz_merge, envz_remove,
envz_strip - environment string support
Standard C library (libc, -lc)
#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);
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.
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.
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() │ │ │
└─────────────────────────────────────┴───────────────┴─────────┘
GNU.
#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);
}
argz_add(3)
This page is part of the man-pages (Linux kernel and C library
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2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
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man-pages@man7.org
Linux man-pages 6.9.1 2024-06-15 envz_add(3)
Pages that refer to this page: argz_add(3)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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