m_env.3

牛顿插值方法求解多项式的系数

.\"(c) Copyright 1992 by Panagiotis Tsirigotis
.\"All rights reserved.  The file named COPYRIGHT specifies the terms 
.\"and conditions for redistribution.
.\"
.\" $Id: m_env.3,v 1.1.1.1 2003/02/19 17:29:27 bbraun Exp $
.TH ENV 3L "20 October 1992"
.SH NAME
env_create, env_destroy, env_make, env_addvar, env_addstr, env_remvar, env_lookup, env_getvars -- environment manipulation functions
.SH SYNOPSIS
.LP
.nf
.ft B
#include "m_env.h"
.LP
.ft B
env_h env_create( env )
env_h env ;
.LP
.ft B
void env_destroy( env )
env_h env ;
.LP
.ft B
env_h env_make( env_strings )
char **env_strings ;
.LP
.ft B
int env_addvar( env, from_env, var )
env_h env ;
env_h from_env ;
char *var ;
.LP
.ft B
int env_addstr( env, str )
env_h env ;
char *str ;
.LP
.ft B
int env_remvar( env, var )
env_h env ;
char *var ;
.LP
.ft B
char **env_getvars( env )
env_h env ;
.SH DESCRIPTION
This library handles environments. An environment is a set of strings
of the form 
.I "name=value".
In the following, we will use the term string as a synonym of
NUL-terminated array of 
.I char.
.LP
.B env_create()
creates a new environment. The new environment will be empty unless
the argument
.I env
is not
.SB ENV_NULL.
In that case, the new environment will be a duplicate of 
.I env
(i.e. they will contain the same strings).
.LP
.B env_destroy()
destroys the specified environment.
.LP
.B env_make()
creates a new environment which includes the
.I env_strings.
.I env_strings
should be a NULL-terminated array of strings.
.LP
.B env_addvar()
adds the specified variable
.I var
to
.I env.
The variable value is obtained from the environment
.I from_env.
If the variable exists already in 
.I env
the old value is replaced with the new value.
.LP
.B env_addstr()
adds a string of the form
.I "name=value"
to
.I env.
.LP
.B env_remvar()
removes the specified variable
.I var
from the environment
.I env.
.LP
.B env_lookup()
searches
.I env
for variable
.I var.
It returns a string of the form
.I "name=value"
where
.I name
is the name of the variable
(i.e. it is equal to
.I var).
.LP
.B env_getvars
returns a NULL-terminated array of strings of the form
.I "name=value".
.SH "RETURN VALUES"
In case of error, all calls will place an error code in the global variable
.I env_errno.
Possible error codes:
.TP 15
.SB ENV_ENOMEM
out of memory
.TP
.SB ENV_EBADVAR
variable is not in environment
.TP
.SB ENV_EBADSTRING
string is not well-formed (i.e. is not of the form \fIname=value\fR).
.LP
.B env_create()
returns a handle or 
.SM ENV_NULL
if it fails.
.LP
.B env_make()
returns a handle or 
.SM ENV_NULL
if it fails.
.LP
.B env_addvar()
returns
.SM ENV_OK
on success or
.SM ENV_ERR
on failure.
.LP
.B env_addstr()
returns
.SM ENV_OK
on success or
.SM ENV_ERR
on failure.
.LP
.B env_remvar()
returns
.SM ENV_OK
on success or
.SM ENV_ERR
if the variable is not part of the environment.
.LP
.B env_loopkup()
returns a string on success or
.SM NULL
on failure.
.SH "SEE ALSO"
environ(5)