Originální popis anglicky:
putenv - change or add a value to an environment
Návod, kniha: POSIX Programmer's Manual
#include <stdlib.h>
int putenv(char *
string);
The
putenv() function shall use the
string argument to set
environment variable values. The
string argument should point to a
string of the form "
name=
value ". The
putenv() function shall make the value of the environment variable
name equal to
value by altering an existing variable or creating
a new one. In either case, the string pointed to by
string shall become
part of the environment, so altering the string shall change the environment.
The space used by
string is no longer used once a new string which
defines
name is passed to
putenv().
The
putenv() function need not be reentrant. A function that is not
required to be reentrant is not required to be thread-safe.
Upon successful completion,
putenv() shall return 0; otherwise, it shall
return a non-zero value and set
errno to indicate the error.
The
putenv() function may fail if:
- ENOMEM
- Insufficient memory was available.
The following sections are informative.
The following example changes the value of the
HOME environment variable
to the value
/usr/home.
#include <stdlib.h>
...
static char *var = "HOME=/usr/home";
int ret;
ret = putenv(var);
The
putenv() function manipulates the environment pointed to by
environ, and can be used in conjunction with
getenv().
See
exec() , for restrictions on changing the environment in
multi-threaded applications.
This routine may use
malloc() to enlarge the environment.
A potential error is to call
putenv() with an automatic variable as the
argument, then return from the calling function while
string is still
part of the environment.
The
setenv() function is preferred over this function.
The standard developers noted that
putenv() is the only function
available to add to the environment without permitting memory leaks.
None.
exec() ,
getenv() ,
malloc() ,
setenv() , the Base
Definitions volume of IEEE Std 1003.1-2001,
<stdlib.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
