setenv(3C)setenv(3C)NAMEsetenv(), unsetenv() - add, update or remove an environment variable
SYNOPSIS
Parameters
envname Points to a string containing the name of an environ‐
ment 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 val‐
ues are non-zero and zero. If the environment vari‐
able does not exist in the environment, then the value
of this variable is ignored.
DESCRIPTION
and functions update the environment of the calling process.
If envname does not exist, the function ignores the value of overwrite
and adds the variable envname to the environment with the value envval.
If envname exists and overwrite is non-zero, then the variable envname
is updated with the new value envval. If envname exists and overwrite
is zero, then the variable is not updated, and the function is consid‐
ered to have completed successfully.
The function deletes the variable envname from the environment, if it
exists. If the envname variable does not exist in the current environ‐
ment, the environment is unchanged, and the function is considered to
have completed successfully.
If the application modifies environ or the pointers to which it points,
the behavior of and is undefined.
EXTERNAL INFLUENCES
Locale
The 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 and functions return zero on success; otherwise they return and set
to indicate the error.
ERRORS
If the function fails, is set to one of the following values:
Sufficient memory is not available to add a variable or its
value to
the environment.
The envname argument is a null pointer, points to an
empty string, or points to a string containing an
equal character.
If the function fails, is set to the following value:
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 to the current envi‐
ronment.
The following code updates the variable
The following code removes the variable from the current environment.
WARNINGS
The and functions manipulate the environment pointed to by environ, and
can be used in conjunction with However, envp (the third argument to
main) is not changed.
The uses to enlarge the environment (see malloc(3C)).
After the or function is called, environment variables may not be in
alphabetical order.
AUTHOR
and were developed by HP.
SEE ALSOexec(2), getenv(3C), malloc(3C), putenv(3C), environ(5),
thread_safety(5).
STANDARDS CONFORMANCEsetenv(3C)
