► |  | The Racket Reference

1 | Language Model
2 | Syntactic Forms
3 | Datatypes
4 | Structures
5 | Classes and Objects
6 | Units
7 | Contracts
8 | Pattern Matching
9 | Control Flow
10 | Concurrency and Parallelism
11 | Macros
12 | Input and Output
13 | Reflection and Security
14 | Operating System
15 | Memory Management
16 | Unsafe Operations
17 | Running Racket
| Bibliography
| Index

▼ | 14 | Operating System

14.1 | Paths
14.2 | Filesystem
14.3 | Networking
14.4 | Processes
14.5 | Logging
14.6 | Time
14.7 | Environment and Runtime Information
14.8 | Command-Line Parsing

On this page:

getenv
putenv
system-type
system-language+ country
system-library-subpath
version
banner
current-command-line-arguments
current-thread-initial-stack-size
vector-set-performance-stats!

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#### 14.7`` Environment and Runtime Information

> procedure (getenv name) → (or/c string? #f)
> name : string?

Gets the value of an operating system environment variable. The name argument cannot contain a null character; if an environment variable named by name exists, its value is returned (as a string); otherwise, #f is returned.

> procedure (putenv name value) → boolean?
> name : string?
> value : string?

Sets the value of an operating system environment variable. The name and value arguments are strings that cannot contain a null character; the environment variable named by name is set to value. The return value is #t if the assignment succeeds, #f otherwise.

> procedure (system-type [mode]) → (or/c symbol? string? bytes?)
> mode : (or/c 'os 'gc 'link 'so-suffix 'machine) = 'os

Returns information about the operating system, build mode, or machine for a running Racket.

In 'os mode, the possible symbol results are:

- 'unix

- 'windows

- 'macosx

In 'gc mode, the possible symbol results are:

- 'cgc

- '3m

In 'link mode, the possible symbol results are:

- 'static (Unix)

- 'shared (Unix)

- 'dll (Windows)

- 'framework (Mac OS X)

Future ports of Racket may expand the list of 'os, 'gc, and 'link results.

In 'so-suffix mode, then the result is a byte string that represents the file extension used for shared objects on the current platform. The byte string starts with a period, so it is suitable as a second argument to path-replace-suffix.

In 'machine mode, then the result is a string, which contains further details about the current machine in a platform-specific format.

> procedure (system-language+country) → string?

Returns a string to identify the current user’s language and country.

On Unix and Mac OS X, the string is five characters: two lowercase ASCII letters for the language, an underscore, and two uppercase ASCII letters for the country. On Windows, the string can be arbitrarily long, but the language and country are in English (all ASCII letters or spaces) separated by an underscore.

On Unix, the result is determined by checking the LC_ALL, LC_TYPE, and LANG environment variables, in that order (and the result is used if the environment variable’s value starts with two lowercase ASCII letters, an underscore, and two uppercase ASCII letters, followed by either nothing or a period). On Windows and Mac OS X, the result is determined by system calls.

> procedure (system-library-subpath [mode]) → path?
> mode : (or/c 'cgc '3m #f) = (system-type 'gc)

Returns a relative directory path. This string can be used to build paths to system-specific files. For example, when Racket is running on Solaris on a Sparc architecture, the subpath starts "sparc-solaris", while the subpath for Windows on an i386 architecture starts "win32\\i386".

The optional mode argument specifies the relevant garbage-collection variant, which one of the possible results of (system-type 'gc): 'cgc or '3m. It can also be #f, in which case the result is independent of the garbage-collection variant.

> procedure (version) → (and/c string? immutable?)

Returns an string indicating the currently executing version of Racket.

> procedure (banner) → (and/c string? immutable?)

Returns an immutable string for Racket’s start-up banner text (or the banner text for an embedding program, such as GRacket). The banner string ends with a newline.

> parameter (current-command-line-arguments)
> → (vectorof (and/c string? immutable?))
> (current-command-line-arguments argv) → void?
> argv : (vectorof (and/c string? immutable?))

A parameter that is initialized with command-line arguments when Racket starts (not including any command-line arguments that were treated as flags for the system).

> parameter (current-thread-initial-stack-size) → exact-positive-integer?
> (current-thread-initial-stack-size size) → void?
> size : exact-positive-integer?

A parameter that provides a hint about how much space to reserve for a newly created thread’s local variables. The actual space used by a computation is affected by JIT compilation, but it is otherwise platform-independent.

> procedure (vector-set-performance-stats! results [thd]) → void?
> | results |  | : |  |
> (and/c vector?
> (not/c immutable?))
> thd : (or/c thread? #f) = #f

Sets elements in results to report current performance statistics. If thd is not #f, a particular set of thread-specific statistics are reported, otherwise a different set of global statics are reported.

For global statistics, up to 11 elements are set in the vector, starting from the beginning. If results has n elements where n < 11, then the n elements are set to the first n performance-statistics values. The reported statistics values are as follows, in the order that they are set within results:

- 0: The same value as returned by current-process-milliseconds.

- 1: The same value as returned by current-milliseconds.

- 2: The same value as returned by current-gc-milliseconds.

- 3: The number of garbage collections performed since start-up.

- 4: The number of thread context switches performed since start-up.

- 5: The number of internal stack overflows handled since start-up.

- 6: The number of threads currently scheduled for execution (i.e., threads that are running, not suspended, and not unscheduled due to a synchronization).

- 7: The number of syntax objects read from compiled code since start-up.

- 8: The number of hash-table searches performed. When this counter reaches the maximum value of a fixnum, it overflows to the most negative fixnum.

- 9: The number of additional hash slots searched to complete hash searches (using double hashing). When this counter reaches the maximum value of a fixnum, it overflows to the most negative fixnum.

- 10: The number of bytes allocated for machine code that is not reported by current-memory-use.

For thread-specific statistics, up to 4 elements are set in the vector:

- 0: #t if the thread is running, #f otherwise (same result as thread-running?).

- 1: #t if the thread has terminated, #f otherwise (same result as thread-dead?).

- 2: #t if the thread is currently blocked on a synchronizable event (or sleeping for some number of milliseconds), #f otherwise.

- 3: The number of bytes currently in use for the thread’s continuation.

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