putenv(3) — AIX PS/2 1.2.1



PUTENV(3,L)                 AIX Technical Reference                 PUTENV(3,L)



-------------------------------------------------------------------------------
putenv



PURPOSE

Sets an environment variable.

LIBRARY

Standard C Library (libc.a)

SYNTAX

int putenv (str)
char *str;

DESCRIPTION

The putenv subroutine sets the value of an environment variable by altering an
existing variable or by creating a new one.  The str parameter points to a
string of the form name=value, where name is the environment variable and value
is the new value for it.

The memory space pointed to by the str parameter becomes part of the
environment, so that altering the string effectively changes part of the
environment.  The space is no longer used after the value of the environment
variable is changed by calling putenv again.

Warning:  Unpredictable results can occur if a subroutine passes putenv a
pointer to an automatic variable and then returns while the variable is still
part of the environment.

Note:  The putenv subroutine manipulates the environment pointed to by the
       environ external variable, and it can be used in conjunction with
       getenv.  However, envp, the third parameter to main, is not changed.
       See "exec:  execl, execv, execle, execve, execlp, execvp" for more
       information about environ and envp.

The putenv subroutine uses malloc to enlarge the environment.

After putenv is called, environment variables are not necessarily in
alphabetical order.

RETURN VALUE

Upon successful completion, a value of 0 is returned.  If malloc is unable to
obtain sufficient space to expand the environment, then putenv returns a value
of -1.





Processed November 7, 1990        PUTENV(3,L)                                 1



PUTENV(3,L)                 AIX Technical Reference                 PUTENV(3,L)



ERROR CONDITIONS

The putenv subroutine fails if the following is true:

ENOMEM    Insufficient memory was available.

RELATED INFORMATION

In this book:  "exec:  execl, execv, execle, execve, execlp, execvp,"  "getenv,
NLgetenv,"  "malloc, free, realloc, calloc, valloc, alloca, mallopt, mallinfo,"
and "environment."












































Processed November 7, 1990        PUTENV(3,L)                                 2

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