HP-UX Reference (11i v2 07/12) - 3 Library Functions N-Z (vol 7)

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setenv(3C) setenv(3C)
NAME
setenv(), unsetenv() - add, update or remove an environment variable
SYNOPSIS
#include <stdlib.h>
int setenv(const char *envname, const char *envval, int overwrite);
int unsetenv(const char *envname);
Parameters
envname Points to a string containing the name of an environment variable to be added or altered.
This should not be a NULL pointer or null string, and the string should not contain an
equal (=) character.
envval Points to a string containing the value to be set for the variable envname.
overwrite Indicates whether to overwrite the value of envname variable or not, if it already exists.
Expected values are non-zero and zero. If the environment variable does not exist in the
environment, then the value of this variable is ignored.
DESCRIPTION
To use these functions, compile with the option
-I/usr/include/ep
and link in the libcext library by
specifying
-lcext, for example:
cc -I/usr/include/ep [flag]... cfile[...] -lcext [...]
setenv()
and unsetenv() functions update the environment of the calling process.
If envname does not exist, the setenv() function ignores the value of overwrite and adds the variable
envname to the environment with the value envval.Ifenvname exists and overwrite is non-zero, then the
variable envname is updated with the new value envval.Ifenvname exists and overwrite is zero, then the
variable is not updated, and the function is considered to have completed successfully.
The
unsetenv() function deletes the variable envname from the environment, if it exists. If the
envname variable does not exist in the current environment, the environment is unchanged, and the func-
tion is considered to have completed successfully.
If the application modifies environ or the pointers to which it points, the behavior of
setenv() and
unsetenv() is undefined.
EXTERNAL INFLUENCES
Locale
The LC_CTYPE category determines the interpretation of characters in string as single- and/or multi-byte
characters.
International Code Set Support
Single- and multi-byte character code sets are supported.
RETURN VALUE
The
setenv() and unsetenv() functions return zero on success; otherwise they return -1 and set
errno to indicate the error.
ERRORS
If the setenv() function fails, errno is set to one of the following values:
[ENOMEM] Sufficient memory is not available to add a variable or its value to the environment.
[EINVAL] The envname argument is a null pointer, points to an empty string, or points to a
string containing an equal (=) character.
If the unsetenv() function fails, errno is set to the following value:
[EINVAL] The envname argument is a null pointer, points to an empty string, or points to a
string containing an equal (=) character.
EXAMPLES
The following code adds a new environment variable NEWHOME to the current environment.
398 Hewlett-Packard Company − 1 − HP-UX 11i Version 2: December 2007 Update