15.7 Environment Variables (original) (raw)

15.7 Environment Variables🔗ℹ

An environment variable set encapsulates a partial mapping from byte strings to byte strings. A Racket process’s initialenvironment variable set is connected to the operating system’s environment variables: accesses or changes to the set read or change operating-system environment variables for the Racket process.

Since Windows environment variables are case-insensitive,environment variable set’s key byte strings on Windows are case-folded. More precisely, key byte strings are coerced to a UTF-8 encoding of characters that are converted to lowercase viastring-locale-downcase.

The current environment variable set, which is determined by the current-environment-variables parameter, is propagated to a subprocess when the subprocess is created.

Returns #t if v is an environment variable set, #f otherwise.

A parameter that determines the environment variable setthat is propagated to a subprocess and that is used as the default set for getenv and putenv.

Returns #t if v is a byte string and if it is valid for an environment variable name. An environment variable name must contain no bytes with the value 0 or 61, where61 is (char->integer #\=). On Windows, an environment variable name also must have a non-zero length.

Creates a fresh environment variable set that is initialized with the given name to val mappings.

Returns the mapping for name in env, returning#f if name has no mapping.

Normally, name should be a byte-string encoding of a string using the default encoding of the current locale. On Windows,name is coerced to a UTF-8 encoding and case-normalized.

Changes the mapping for name in env tomaybe-bstr. If maybe-bstr is #f andenv is the initial environment variable set of the Racket process, then the operating system environment-variable mapping for name is removed.

Normally, name and maybe-bstr should be a byte-string encoding of a string using the default encoding of the current locale. On Windows, name is coerced to a UTF-8 encoding and case-normalized, andmaybe-bstr is coerced to a UTF-8 encoding if env is the initial environment variable set of the Racket process.

On success, the result of environment-variables-set! is#. If env is the initial environment variable set of the Racket process, then attempting to adjust the operating system environment-variable mapping might fail for some reason, in which case fail is called in tail position with respect to theenvironment-variables-set!. The default fail raises an exception.

Returns a list of byte strings that corresponds to names mapped byenv.

Returns an environment variable set that is initialized with the same mappings as env.

Convenience wrappers for environment-variables-ref andenvironment-variables-set! that convert between strings and byte strings using the current locale’s default encoding (using#\? as the replacement character for encoding errors) and always using the current environment variable set fromcurrent-environment-variables. The putenv function returns #t for success and #f for failure.

Returns #t if v is a string and if its encoding using the current locale’s encoding is valid for an environment variable name according to bytes-environment-variable-name?.