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putenv(3c) [opensolaris man page]

putenv(3C)						   Standard C Library Functions 						putenv(3C)

NAME
putenv - change or add value to environment SYNOPSIS
#include <stdlib.h> int putenv(char *string); DESCRIPTION
The putenv() function makes 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 becomes part of the environment, so altering the string will change the environment. The string argument points to a string of the form name=value. The space used by string is no longer used once a new string-defining name is passed to putenv(). The putenv() function uses malloc(3C) to enlarge the environment. After putenv() is called, environment variables are not in alphabetical order. RETURN VALUES
Upon successful completion, putenv() returns 0. Otherwise, it returns a non-zero value and sets errno to indicate the error. ERRORS
The putenv() function may fail if: ENOMEM Insufficient memory was available. USAGE
The putenv() function can be safely called from multithreaded programs. Caution must be exercised when using this function and getenv(3C) in multithreaded programs. These functions examine and modify the environment list, which is shared by all threads in a program. The sys- tem prevents the list from being accessed simultaneously by two different threads. It does not, however, prevent two threads from succes- sively accessing the environment list using putenv() or getenv(). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |Safe | +-----------------------------+-----------------------------+ SEE ALSO
exec(2), getenv(3C), malloc(3C), attributes(5), environ(5), standards(5) WARNINGS
The string argument should not be an automatic variable. It should be declared static if it is declared within a function because it can- not be automatically declared. A potential error is to call putenv() with a pointer to an automatic variable as the argument and to then exit the calling function while string is still part of the environment. SunOS 5.11 7 Aug 2004 putenv(3C)

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PUTENV(3)                                                    Linux Programmer's Manual                                                   PUTENV(3)

NAME
putenv - change or add an environment variable SYNOPSIS
#include <stdlib.h> int putenv(char *string); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): putenv(): _XOPEN_SOURCE || /* Glibc since 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _SVID_SOURCE DESCRIPTION
The putenv() function adds or changes the value of environment variables. The argument string is of the form name=value. If name does not already exist in the environment, then string is added to the environment. If name does exist, then the value of name in the environment is changed to value. The string pointed to by string becomes part of the environment, so altering the string changes the environment. RETURN VALUE
The putenv() function returns zero on success, or nonzero if an error occurs. In the event of an error, errno is set to indicate the cause. ERRORS
ENOMEM Insufficient space to allocate new environment. ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7). +----------+---------------+---------------------+ |Interface | Attribute | Value | +----------+---------------+---------------------+ |putenv() | Thread safety | MT-Unsafe const:env | +----------+---------------+---------------------+ CONFORMING TO
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD. NOTES
The putenv() function is not required to be reentrant, and the one in glibc 2.0 is not, but the glibc 2.1 version is. Since version 2.1.2, the glibc implementation conforms to SUSv2: the pointer string given to putenv() is used. In particular, this string becomes part of the environment; changing it later will change the environment. (Thus, it is an error is to call putenv() with an auto- matic variable as the argument, then return from the calling function while string is still part of the environment.) However, glibc ver- sions 2.0 to 2.1.1 differ: a copy of the string is used. On the one hand this causes a memory leak, and on the other hand it violates SUSv2. The 4.4BSD version, like glibc 2.0, uses a copy. SUSv2 removes the const from the prototype, and so does glibc 2.1.3. SEE ALSO
clearenv(3), getenv(3), setenv(3), unsetenv(3), environ(7) COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/. GNU 2016-03-15 PUTENV(3)
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