putenv(S)                      6 January 1993                      putenv(S)


 Name

    putenv - change or add value to environment

 Syntax


    cc  . . .  -lc


    int putenv (string)
    char *string;


 Description

    string points to a string of the form ``name = value''.  The putenv func-
    tion 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 changes the environment.  The space used by string is no
    longer used once a new string defining name is passed to putenv.

 Diagnostics

    The putenv function returns non-zero if it was unable to obtain enough
    space via malloc for an expanded environment, otherwise zero.

 Warnings

    The putenv function manipulates the environment pointed to by environ,
    and can be used in conjunction with getenv.  However, envp (the third
    argument to main) is not changed.  After putenv is called, environmental
    variables are not in alphabetical order.

    A potential error is to call putenv with an automatic variable as the
    argument, then exit the calling function while string is still part of
    the environment.

    This routine uses malloc(S) to enlarge the environment.

 See also

    environ(M), exec(S), getenv(S), malloc(S)

 Standards conformance

    putenv is conformant with:
    AT&T SVID Issue 2;
    and X/Open Portability Guide, Issue 3, 1989.