---
name: "envz_add"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/envz_add"
---

# envz\_add(3)

environment string support

## 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)](/argz_add/3.md). 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)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **envz\_add**(), **envz\_entry**(), **envz\_get**(), **envz\_merge**(), **envz\_remove**(), **envz\_strip**() | Thread safety | MT-Safe |

## 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)](/argz_add/3.md)