envz(3) Linux Man Page - System Grab Bag

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 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). allbox; lbx lb lb T{ envz_add()envz_entry()envz_get()envz_merge()envz_remove()envz_strip()

Interface	Attribute	Value
T}	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\en", str);
    str = envz_get(*envp, e_len, "HOME");
    printf("%s\en", str);
    exit(EXIT_SUCCESS);
}