src/doc/src/reference/config.md

   1 ## Configuration
   2
   3 This document explains how Cargo’s configuration system works, as well as
   4 available keys or configuration. For configuration of a package through its
   5 manifest, see the [manifest format](manifest.md).
   6
   7 ### Hierarchical structure
   8
   9 Cargo allows local configuration for a particular package as well as global
  10 configuration. It looks for configuration files in the current directory and
  11 all parent directories. If, for example, Cargo were invoked in
  12 `/projects/foo/bar/baz`, then the following configuration files would be
  13 probed for and unified in this order:
  14
  15 * `/projects/foo/bar/baz/.cargo/config.toml`
  16 * `/projects/foo/bar/.cargo/config.toml`
  17 * `/projects/foo/.cargo/config.toml`
  18 * `/projects/.cargo/config.toml`
  19 * `/.cargo/config.toml`
  20 * `$CARGO_HOME/config.toml` which defaults to:
  21     * Windows: `%USERPROFILE%\.cargo\config.toml`
  22     * Unix: `$HOME/.cargo/config.toml`
  23
  24 With this structure, you can specify configuration per-package, and even
  25 possibly check it into version control. You can also specify personal defaults
  26 with a configuration file in your home directory.
  27
  28 If a key is specified in multiple config files, the values will get merged
  29 together. Numbers, strings, and booleans will use the value in the deeper
  30 config directory taking precedence over ancestor directories, where the
  31 home directory is the lowest priority. Arrays will be joined together.
  32
  33 At present, when being invoked from a workspace, Cargo does not read config
  34 files from crates within the workspace. i.e. if a workspace has two crates in
  35 it, named `/projects/foo/bar/baz/mylib` and `/projects/foo/bar/baz/mybin`, and
  36 there are Cargo configs at `/projects/foo/bar/baz/mylib/.cargo/config.toml`
  37 and `/projects/foo/bar/baz/mybin/.cargo/config.toml`, Cargo does not read
  38 those configuration files if it is invoked from the workspace root
  39 (`/projects/foo/bar/baz/`).
  40
  41 > **Note:** Cargo also reads config files without the `.toml` extension, such as
  42 > `.cargo/config`. Support for the `.toml` extension was added in version 1.39
  43 > and is the preferred form. If both files exist, Cargo will use the file
  44 > without the extension.
  45
  46 ### Configuration format
  47
  48 Configuration files are written in the [TOML format][toml] (like the
  49 manifest), with simple key-value pairs inside of sections (tables). The
  50 following is a quick overview of all settings, with detailed descriptions
  51 found below.
  52
  53 ```toml
  54 paths = ["/path/to/override"] # path dependency overrides
  55
  56 [alias]     # command aliases
  57 b = "build"
  58 c = "check"
  59 t = "test"
  60 r = "run"
  61 rr = "run --release"
  62 space_example = ["run", "--release", "--", "\"command list\""]
  63
  64 [build]
  65 jobs = 1                      # number of parallel jobs, defaults to # of CPUs
  66 rustc = "rustc"               # the rust compiler tool
  67 rustc-wrapper = "…"           # run this wrapper instead of `rustc`
  68 rustc-workspace-wrapper = "…" # run this wrapper instead of `rustc` for workspace members
  69 rustdoc = "rustdoc"           # the doc generator tool
  70 target = "triple"             # build for the target triple (ignored by `cargo install`)
  71 target-dir = "target"         # path of where to place all generated artifacts
  72 rustflags = ["…", "…"]        # custom flags to pass to all compiler invocations
  73 rustdocflags = ["…", "…"]     # custom flags to pass to rustdoc
  74 incremental = true            # whether or not to enable incremental compilation
  75 dep-info-basedir = "…"        # path for the base directory for targets in depfiles
  76 pipelining = true             # rustc pipelining
  77
  78 [doc]
  79 browser = "chromium"          # browser to use with `cargo doc --open`,
  80                               # overrides the `BROWSER` environment variable
  81
  82 [env]
  83 # Set ENV_VAR_NAME=value for any process run by Cargo
  84 ENV_VAR_NAME = "value"
  85 # Set even if already present in environment
  86 ENV_VAR_NAME_2 = { value = "value", force = true }
  87 # Value is relative to .cargo directory containing `config.toml`, make absolute
  88 ENV_VAR_NAME_3 = { value = "relative/path", relative = true }
  89
  90 [future-incompat-report]
  91 frequency = 'always' # when to display a notification about a future incompat report
  92
  93 [cargo-new]
  94 vcs = "none"              # VCS to use ('git', 'hg', 'pijul', 'fossil', 'none')
  95
  96 [http]
  97 debug = false               # HTTP debugging
  98 proxy = "host:port"         # HTTP proxy in libcurl format
  99 ssl-version = "tlsv1.3"     # TLS version to use
 100 ssl-version.max = "tlsv1.3" # maximum TLS version
 101 ssl-version.min = "tlsv1.1" # minimum TLS version
 102 timeout = 30                # timeout for each HTTP request, in seconds
 103 low-speed-limit = 10        # network timeout threshold (bytes/sec)
 104 cainfo = "cert.pem"         # path to Certificate Authority (CA) bundle
 105 check-revoke = true         # check for SSL certificate revocation
 106 multiplexing = true         # HTTP/2 multiplexing
 107 user-agent = "…"            # the user-agent header
 108
 109 [install]
 110 root = "/some/path"         # `cargo install` destination directory
 111
 112 [net]
 113 retry = 2                   # network retries
 114 git-fetch-with-cli = true   # use the `git` executable for git operations
 115 offline = true              # do not access the network
 116
 117 [patch.<registry>]
 118 # Same keys as for [patch] in Cargo.toml
 119
 120 [profile.<name>]         # Modify profile settings via config.
 121 opt-level = 0            # Optimization level.
 122 debug = true             # Include debug info.
 123 split-debuginfo = '...'  # Debug info splitting behavior.
 124 debug-assertions = true  # Enables debug assertions.
 125 overflow-checks = true   # Enables runtime integer overflow checks.
 126 lto = false              # Sets link-time optimization.
 127 panic = 'unwind'         # The panic strategy.
 128 incremental = true       # Incremental compilation.
 129 codegen-units = 16       # Number of code generation units.
 130 rpath = false            # Sets the rpath linking option.
 131 [profile.<name>.build-override]  # Overrides build-script settings.
 132 # Same keys for a normal profile.
 133 [profile.<name>.package.<name>]  # Override profile for a package.
 134 # Same keys for a normal profile (minus `panic`, `lto`, and `rpath`).
 135
 136 [registries.<name>]  # registries other than crates.io
 137 index = "…"          # URL of the registry index
 138 token = "…"          # authentication token for the registry
 139
 140 [registry]
 141 default = "…"        # name of the default registry
 142 token = "…"          # authentication token for crates.io
 143
 144 [source.<name>]      # source definition and replacement
 145 replace-with = "…"   # replace this source with the given named source
 146 directory = "…"      # path to a directory source
 147 registry = "…"       # URL to a registry source
 148 local-registry = "…" # path to a local registry source
 149 git = "…"            # URL of a git repository source
 150 branch = "…"         # branch name for the git repository
 151 tag = "…"            # tag name for the git repository
 152 rev = "…"            # revision for the git repository
 153
 154 [target.<triple>]
 155 linker = "…"            # linker to use
 156 runner = "…"            # wrapper to run executables
 157 rustflags = ["…", "…"]  # custom flags for `rustc`
 158
 159 [target.<cfg>]
 160 runner = "…"            # wrapper to run executables
 161 rustflags = ["…", "…"]  # custom flags for `rustc`
 162
 163 [target.<triple>.<links>] # `links` build script override
 164 rustc-link-lib = ["foo"]
 165 rustc-link-search = ["/path/to/foo"]
 166 rustc-flags = ["-L", "/some/path"]
 167 rustc-cfg = ['key="value"']
 168 rustc-env = {key = "value"}
 169 rustc-cdylib-link-arg = ["…"]
 170 metadata_key1 = "value"
 171 metadata_key2 = "value"
 172
 173 [term]
 174 verbose = false        # whether cargo provides verbose output
 175 color = 'auto'         # whether cargo colorizes output
 176 progress.when = 'auto' # whether cargo shows progress bar
 177 progress.width = 80    # width of progress bar
 178 ```
 179
 180 ### Environment variables
 181
 182 Cargo can also be configured through environment variables in addition to the
 183 TOML configuration files. For each configuration key of the form `foo.bar` the
 184 environment variable `CARGO_FOO_BAR` can also be used to define the value.
 185 Keys are converted to uppercase, dots and dashes are converted to underscores.
 186 For example the `target.x86_64-unknown-linux-gnu.runner` key can also be
 187 defined by the `CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUNNER` environment
 188 variable.
 189
 190 Environment variables will take precedence over TOML configuration files.
 191 Currently only integer, boolean, string and some array values are supported to
 192 be defined by environment variables. Descriptions below indicate which keys
 193 support environment variables.
 194
 195 In addition to the system above, Cargo recognizes a few other specific
 196 [environment variables][env].
 197
 198 ### Config-relative paths
 199
 200 Paths in config files may be absolute, relative, or a bare name without any
 201 path separators. Paths for executables without a path separator will use the
 202 `PATH` environment variable to search for the executable. Paths for
 203 non-executables will be relative to where the config value is defined. For
 204 config files, that is relative to the parent directory of the `.cargo`
 205 directory where the value was defined. For environment variables it is
 206 relative to the current working directory.
 207
 208 ```toml
 209 # Relative path examples.
 210
 211 [target.x86_64-unknown-linux-gnu]
 212 runner = "foo"  # Searches `PATH` for `foo`.
 213
 214 [source.vendored-sources]
 215 # Directory is relative to the parent where `.cargo/config.toml` is located.
 216 # For example, `/my/project/.cargo/config.toml` would result in `/my/project/vendor`.
 217 directory = "vendor"
 218 ```
 219
 220 ### Executable paths with arguments
 221
 222 Some Cargo commands invoke external programs, which can be configured as a path
 223 and some number of arguments.
 224
 225 The value may be an array of strings like `['/path/to/program', 'somearg']` or
 226 a space-separated string like `'/path/to/program somearg'`. If the path to the
 227 executable contains a space, the list form must be used.
 228
 229 If Cargo is passing other arguments to the program such as a path to open or
 230 run, they will be passed after the last specified argument in the value of an
 231 option of this format. If the specified program does not have path separators,
 232 Cargo will search `PATH` for its executable.
 233
 234 ### Credentials
 235
 236 Configuration values with sensitive information are stored in the
 237 `$CARGO_HOME/credentials.toml` file. This file is automatically created and updated
 238 by [`cargo login`]. It follows the same format as Cargo config files.
 239
 240 ```toml
 241 [registry]
 242 token = "…"   # Access token for crates.io
 243
 244 [registries.<name>]
 245 token = "…"   # Access token for the named registry
 246 ```
 247
 248 Tokens are used by some Cargo commands such as [`cargo publish`] for
 249 authenticating with remote registries. Care should be taken to protect the
 250 tokens and to keep them secret.
 251
 252 As with most other config values, tokens may be specified with environment
 253 variables. The token for [crates.io] may be specified with the
 254 `CARGO_REGISTRY_TOKEN` environment variable. Tokens for other registries may
 255 be specified with environment variables of the form
 256 `CARGO_REGISTRIES_<name>_TOKEN` where `<name>` is the name of the registry in
 257 all capital letters.
 258
 259 ### Configuration keys
 260
 261 This section documents all configuration keys. The description for keys with
 262 variable parts are annotated with angled brackets like `target.<triple>` where
 263 the `<triple>` part can be any target triple like
 264 `target.x86_64-pc-windows-msvc`.
 265
 266 #### `paths`
 267 * Type: array of strings (paths)
 268 * Default: none
 269 * Environment: not supported
 270
 271 An array of paths to local packages which are to be used as overrides for
 272 dependencies. For more information see the [Overriding Dependencies
 273 guide](overriding-dependencies.md#paths-overrides).
 274
 275 #### `[alias]`
 276 * Type: string or array of strings
 277 * Default: see below
 278 * Environment: `CARGO_ALIAS_<name>`
 279
 280 The `[alias]` table defines CLI command aliases. For example, running `cargo
 281 b` is an alias for running `cargo build`. Each key in the table is the
 282 subcommand, and the value is the actual command to run. The value may be an
 283 array of strings, where the first element is the command and the following are
 284 arguments. It may also be a string, which will be split on spaces into
 285 subcommand and arguments. The following aliases are built-in to Cargo:
 286
 287 ```toml
 288 [alias]
 289 b = "build"
 290 c = "check"
 291 d = "doc"
 292 t = "test"
 293 r = "run"
 294 ```
 295
 296 Aliases are not allowed to redefine existing built-in commands.
 297
 298 #### `[build]`
 299
 300 The `[build]` table controls build-time operations and compiler settings.
 301
 302 ##### `build.jobs`
 303 * Type: integer
 304 * Default: number of logical CPUs
 305 * Environment: `CARGO_BUILD_JOBS`
 306
 307 Sets the maximum number of compiler processes to run in parallel.
 308
 309 Can be overridden with the `--jobs` CLI option.
 310
 311 ##### `build.rustc`
 312 * Type: string (program path)
 313 * Default: "rustc"
 314 * Environment: `CARGO_BUILD_RUSTC` or `RUSTC`
 315
 316 Sets the executable to use for `rustc`.
 317
 318 ##### `build.rustc-wrapper`
 319 * Type: string (program path)
 320 * Default: none
 321 * Environment: `CARGO_BUILD_RUSTC_WRAPPER` or `RUSTC_WRAPPER`
 322
 323 Sets a wrapper to execute instead of `rustc`. The first argument passed to the
 324 wrapper is the path to the actual `rustc`.
 325
 326 ##### `build.rustc-workspace-wrapper`
 327 * Type: string (program path)
 328 * Default: none
 329 * Environment: `CARGO_BUILD_RUSTC_WORKSPACE_WRAPPER` or `RUSTC_WORKSPACE_WRAPPER`
 330
 331 Sets a wrapper to execute instead of `rustc`, for workspace members only.
 332 The first argument passed to the wrapper is the path to the actual `rustc`.
 333 It affects the filename hash so that artifacts produced by the wrapper are cached separately.
 334
 335 ##### `build.rustdoc`
 336 * Type: string (program path)
 337 * Default: "rustdoc"
 338 * Environment: `CARGO_BUILD_RUSTDOC` or `RUSTDOC`
 339
 340 Sets the executable to use for `rustdoc`.
 341
 342 ##### `build.target`
 343 * Type: string
 344 * Default: host platform
 345 * Environment: `CARGO_BUILD_TARGET`
 346
 347 The default target platform triple to compile to.
 348
 349 This may also be a relative path to a `.json` target spec file.
 350
 351 Can be overridden with the `--target` CLI option.
 352
 353 ##### `build.target-dir`
 354 * Type: string (path)
 355 * Default: "target"
 356 * Environment: `CARGO_BUILD_TARGET_DIR` or `CARGO_TARGET_DIR`
 357
 358 The path to where all compiler output is placed. The default if not specified
 359 is a directory named `target` located at the root of the workspace.
 360
 361 Can be overridden with the `--target-dir` CLI option.
 362
 363 ##### `build.rustflags`
 364 * Type: string or array of strings
 365 * Default: none
 366 * Environment: `CARGO_BUILD_RUSTFLAGS` or `RUSTFLAGS`
 367
 368 Extra command-line flags to pass to `rustc`. The value may be a array of
 369 strings or a space-separated string.
 370
 371 There are three mutually exclusive sources of extra flags. They are checked in
 372 order, with the first one being used:
 373
 374 1. `RUSTFLAGS` environment variable.
 375 2. All matching `target.<triple>.rustflags` and `target.<cfg>.rustflags`
 376    config entries joined together.
 377 3. `build.rustflags` config value.
 378
 379 Additional flags may also be passed with the [`cargo rustc`] command.
 380
 381 If the `--target` flag (or [`build.target`](#buildtarget)) is used, then the
 382 flags will only be passed to the compiler for the target. Things being built
 383 for the host, such as build scripts or proc macros, will not receive the args.
 384 Without `--target`, the flags will be passed to all compiler invocations
 385 (including build scripts and proc macros) because dependencies are shared. If
 386 you have args that you do not want to pass to build scripts or proc macros and
 387 are building for the host, pass `--target` with the host triple.
 388
 389 It is not recommended to pass in flags that Cargo itself usually manages. For
 390 example, the flags driven by [profiles] are best handled by setting the
 391 appropriate profile setting.
 392
 393 > **Caution**: Due to the low-level nature of passing flags directly to the
 394 > compiler, this may cause a conflict with future versions of Cargo which may
 395 > issue the same or similar flags on its own which may interfere with the
 396 > flags you specify. This is an area where Cargo may not always be backwards
 397 > compatible.
 398
 399 ##### `build.rustdocflags`
 400 * Type: string or array of strings
 401 * Default: none
 402 * Environment: `CARGO_BUILD_RUSTDOCFLAGS` or `RUSTDOCFLAGS`
 403
 404 Extra command-line flags to pass to `rustdoc`. The value may be a array of
 405 strings or a space-separated string.
 406
 407 There are two mutually exclusive sources of extra flags. They are checked in
 408 order, with the first one being used:
 409
 410 1. `RUSTDOCFLAGS` environment variable.
 411 2. `build.rustdocflags` config value.
 412
 413 Additional flags may also be passed with the [`cargo rustdoc`] command.
 414
 415 ##### `build.incremental`
 416 * Type: bool
 417 * Default: from profile
 418 * Environment: `CARGO_BUILD_INCREMENTAL` or `CARGO_INCREMENTAL`
 419
 420 Whether or not to perform [incremental compilation]. The default if not set is
 421 to use the value from the [profile]. Otherwise this overrides the setting of
 422 all profiles.
 423
 424 The `CARGO_INCREMENTAL` environment variable can be set to `1` to force enable
 425 incremental compilation for all profiles, or `0` to disable it. This env var
 426 overrides the config setting.
 427
 428 ##### `build.dep-info-basedir`
 429 * Type: string (path)
 430 * Default: none
 431 * Environment: `CARGO_BUILD_DEP_INFO_BASEDIR`
 432
 433 Strips the given path prefix from [dep
 434 info](../guide/build-cache.md#dep-info-files) file paths. This config setting
 435 is intended to convert absolute paths to relative paths for tools that require
 436 relative paths.
 437
 438 The setting itself is a config-relative path. So, for example, a value of
 439 `"."` would strip all paths starting with the parent directory of the `.cargo`
 440 directory.
 441
 442 ##### `build.pipelining`
 443 * Type: boolean
 444 * Default: true
 445 * Environment: `CARGO_BUILD_PIPELINING`
 446
 447 Controls whether or not build pipelining is used. This allows Cargo to
 448 schedule overlapping invocations of `rustc` in parallel when possible.
 449
 450 #### `[doc]`
 451
 452 The `[doc]` table defines options for the [`cargo doc`] command.
 453
 454 ##### `doc.browser`
 455
 456 * Type: string or array of strings ([program path and args])
 457 * Default: `BROWSER` environment variable, or, if that is missing,
 458   opening the link in a system specific way
 459
 460 This option sets the browser to be used by [`cargo doc`], overriding the
 461 `BROWSER` environment variable when opening documentation with the `--open`
 462 option.
 463
 464 #### `[cargo-new]`
 465
 466 The `[cargo-new]` table defines defaults for the [`cargo new`] command.
 467
 468 ##### `cargo-new.name`
 469
 470 This option is deprecated and unused.
 471
 472 ##### `cargo-new.email`
 473
 474 This option is deprecated and unused.
 475
 476 ##### `cargo-new.vcs`
 477 * Type: string
 478 * Default: "git" or "none"
 479 * Environment: `CARGO_CARGO_NEW_VCS`
 480
 481 Specifies the source control system to use for initializing a new repository.
 482 Valid values are `git`, `hg` (for Mercurial), `pijul`, `fossil` or `none` to
 483 disable this behavior. Defaults to `git`, or `none` if already inside a VCS
 484 repository. Can be overridden with the `--vcs` CLI option.
 485
 486 ### `[env]`
 487
 488 The `[env]` section allows you to set additional environment variables for
 489 build scripts, rustc invocations, `cargo run` and `cargo build`.
 490
 491 ```toml
 492 [env]
 493 OPENSSL_DIR = "/opt/openssl"
 494 ```
 495
 496 By default, the variables specified will not override values that already exist
 497 in the environment. This behavior can be changed by setting the `force` flag.
 498
 499 Setting the `relative` flag evaluates the value as a config-relative path that
 500 is relative to the parent directory of the `.cargo` directory that contains the
 501 `config.toml` file. The value of the environment variable will be the full
 502 absolute path.
 503
 504 ```toml
 505 [env]
 506 TMPDIR = { value = "/home/tmp", force = true }
 507 OPENSSL_DIR = { value = "vendor/openssl", relative = true }
 508 ```
 509
 510 ### `[future-incompat-report]`
 511
 512 The `[future-incompat-report]` table controls setting for [future incompat reporting](future-incompat-report.md)
 513
 514 #### `future-incompat-report.frequency`
 515 * Type: string
 516 * Default: "always"
 517 * Environment: `CARGO_FUTURE_INCOMPAT_REPORT_FREQUENCY`
 518
 519 Controls how often we display a notification to the terminal when a future incompat report is available. Possible values:
 520
 521 * `always` (default): Always display a notification when a command (e.g. `cargo build`) produces a future incompat report
 522 * `never`: Never display a notification
 523
 524 #### `[http]`
 525
 526 The `[http]` table defines settings for HTTP behavior. This includes fetching
 527 crate dependencies and accessing remote git repositories.
 528
 529 ##### `http.debug`
 530 * Type: boolean
 531 * Default: false
 532 * Environment: `CARGO_HTTP_DEBUG`
 533
 534 If `true`, enables debugging of HTTP requests. The debug information can be
 535 seen by setting the `CARGO_LOG=cargo::ops::registry=debug` environment
 536 variable (or use `trace` for even more information).
 537
 538 Be wary when posting logs from this output in a public location. The output
 539 may include headers with authentication tokens which you don't want to leak!
 540 Be sure to review logs before posting them.
 541
 542 ##### `http.proxy`
 543 * Type: string
 544 * Default: none
 545 * Environment: `CARGO_HTTP_PROXY` or `HTTPS_PROXY` or `https_proxy` or `http_proxy`
 546
 547 Sets an HTTP and HTTPS proxy to use. The format is in [libcurl format] as in
 548 `[protocol://]host[:port]`. If not set, Cargo will also check the `http.proxy`
 549 setting in your global git configuration. If none of those are set, the
 550 `HTTPS_PROXY` or `https_proxy` environment variables set the proxy for HTTPS
 551 requests, and `http_proxy` sets it for HTTP requests.
 552
 553 ##### `http.timeout`
 554 * Type: integer
 555 * Default: 30
 556 * Environment: `CARGO_HTTP_TIMEOUT` or `HTTP_TIMEOUT`
 557
 558 Sets the timeout for each HTTP request, in seconds.
 559
 560 ##### `http.cainfo`
 561 * Type: string (path)
 562 * Default: none
 563 * Environment: `CARGO_HTTP_CAINFO`
 564
 565 Path to a Certificate Authority (CA) bundle file, used to verify TLS
 566 certificates. If not specified, Cargo attempts to use the system certificates.
 567
 568 ##### `http.check-revoke`
 569 * Type: boolean
 570 * Default: true (Windows) false (all others)
 571 * Environment: `CARGO_HTTP_CHECK_REVOKE`
 572
 573 This determines whether or not TLS certificate revocation checks should be
 574 performed. This only works on Windows.
 575
 576 ##### `http.ssl-version`
 577 * Type: string or min/max table
 578 * Default: none
 579 * Environment: `CARGO_HTTP_SSL_VERSION`
 580
 581 This sets the minimum TLS version to use. It takes a string, with one of the
 582 possible values of "default", "tlsv1", "tlsv1.0", "tlsv1.1", "tlsv1.2", or
 583 "tlsv1.3".
 584
 585 This may alternatively take a table with two keys, `min` and `max`, which each
 586 take a string value of the same kind that specifies the minimum and maximum
 587 range of TLS versions to use.
 588
 589 The default is a minimum version of "tlsv1.0" and a max of the newest version
 590 supported on your platform, typically "tlsv1.3".
 591
 592 ##### `http.low-speed-limit`
 593 * Type: integer
 594 * Default: 10
 595 * Environment: `CARGO_HTTP_LOW_SPEED_LIMIT`
 596
 597 This setting controls timeout behavior for slow connections. If the average
 598 transfer speed in bytes per second is below the given value for
 599 [`http.timeout`](#httptimeout) seconds (default 30 seconds), then the
 600 connection is considered too slow and Cargo will abort and retry.
 601
 602 ##### `http.multiplexing`
 603 * Type: boolean
 604 * Default: true
 605 * Environment: `CARGO_HTTP_MULTIPLEXING`
 606
 607 When `true`, Cargo will attempt to use the HTTP2 protocol with multiplexing.
 608 This allows multiple requests to use the same connection, usually improving
 609 performance when fetching multiple files. If `false`, Cargo will use HTTP 1.1
 610 without pipelining.
 611
 612 ##### `http.user-agent`
 613 * Type: string
 614 * Default: Cargo's version
 615 * Environment: `CARGO_HTTP_USER_AGENT`
 616
 617 Specifies a custom user-agent header to use. The default if not specified is a
 618 string that includes Cargo's version.
 619
 620 #### `[install]`
 621
 622 The `[install]` table defines defaults for the [`cargo install`] command.
 623
 624 ##### `install.root`
 625 * Type: string (path)
 626 * Default: Cargo's home directory
 627 * Environment: `CARGO_INSTALL_ROOT`
 628
 629 Sets the path to the root directory for installing executables for [`cargo
 630 install`]. Executables go into a `bin` directory underneath the root.
 631
 632 To track information of installed executables, some extra files, such as
 633 `.crates.toml` and `.crates2.json`, are also created under this root.
 634
 635 The default if not specified is Cargo's home directory (default `.cargo` in
 636 your home directory).
 637
 638 Can be overridden with the `--root` command-line option.
 639
 640 #### `[net]`
 641
 642 The `[net]` table controls networking configuration.
 643
 644 ##### `net.retry`
 645 * Type: integer
 646 * Default: 2
 647 * Environment: `CARGO_NET_RETRY`
 648
 649 Number of times to retry possibly spurious network errors.
 650
 651 ##### `net.git-fetch-with-cli`
 652 * Type: boolean
 653 * Default: false
 654 * Environment: `CARGO_NET_GIT_FETCH_WITH_CLI`
 655
 656 If this is `true`, then Cargo will use the `git` executable to fetch registry
 657 indexes and git dependencies. If `false`, then it uses a built-in `git`
 658 library.
 659
 660 Setting this to `true` can be helpful if you have special authentication
 661 requirements that Cargo does not support. See [Git
 662 Authentication](../appendix/git-authentication.md) for more information about
 663 setting up git authentication.
 664
 665 ##### `net.offline`
 666 * Type: boolean
 667 * Default: false
 668 * Environment: `CARGO_NET_OFFLINE`
 669
 670 If this is `true`, then Cargo will avoid accessing the network, and attempt to
 671 proceed with locally cached data. If `false`, Cargo will access the network as
 672 needed, and generate an error if it encounters a network error.
 673
 674 Can be overridden with the `--offline` command-line option.
 675
 676 #### `[patch]`
 677
 678 Just as you can override dependencies using [`[patch]` in
 679 `Cargo.toml`](overriding-dependencies.md#the-patch-section), you can
 680 override them in the cargo configuration file to apply those patches to
 681 any affected build. The format is identical to the one used in
 682 `Cargo.toml`.
 683
 684 Since `.cargo/config.toml` files are not usually checked into source
 685 control, you should prefer patching using `Cargo.toml` where possible to
 686 ensure that other developers can compile your crate in their own
 687 environments. Patching through cargo configuration files is generally
 688 only appropriate when the patch section is automatically generated by an
 689 external build tool.
 690
 691 If a given dependency is patched both in a cargo configuration file and
 692 a `Cargo.toml` file, the patch in the configuration file is used. If
 693 multiple configuration files patch the same dependency, standard cargo
 694 configuration merging is used, which prefers the value defined closest
 695 to the current directory, with `$HOME/.cargo/config.toml` taking the
 696 lowest precedence.
 697
 698 Relative `path` dependencies in such a `[patch]` section are resolved
 699 relative to the configuration file they appear in.
 700
 701 #### `[profile]`
 702
 703 The `[profile]` table can be used to globally change profile settings, and
 704 override settings specified in `Cargo.toml`. It has the same syntax and
 705 options as profiles specified in `Cargo.toml`. See the [Profiles chapter] for
 706 details about the options.
 707
 708 [Profiles chapter]: profiles.md
 709
 710 ##### `[profile.<name>.build-override]`
 711 * Environment: `CARGO_PROFILE_<name>_BUILD_OVERRIDE_<key>`
 712
 713 The build-override table overrides settings for build scripts, proc macros,
 714 and their dependencies. It has the same keys as a normal profile. See the
 715 [overrides section](profiles.md#overrides) for more details.
 716
 717 ##### `[profile.<name>.package.<name>]`
 718 * Environment: not supported
 719
 720 The package table overrides settings for specific packages. It has the same
 721 keys as a normal profile, minus the `panic`, `lto`, and `rpath` settings. See
 722 the [overrides section](profiles.md#overrides) for more details.
 723
 724 ##### `profile.<name>.codegen-units`
 725 * Type: integer
 726 * Default: See profile docs.
 727 * Environment: `CARGO_PROFILE_<name>_CODEGEN_UNITS`
 728
 729 See [codegen-units](profiles.md#codegen-units).
 730
 731 ##### `profile.<name>.debug`
 732 * Type: integer or boolean
 733 * Default: See profile docs.
 734 * Environment: `CARGO_PROFILE_<name>_DEBUG`
 735
 736 See [debug](profiles.md#debug).
 737
 738 ##### `profile.<name>.split-debuginfo`
 739 * Type: string
 740 * Default: See profile docs.
 741 * Environment: `CARGO_PROFILE_<name>_SPLIT_DEBUGINFO`
 742
 743 See [split-debuginfo](profiles.md#split-debuginfo).
 744
 745 ##### `profile.<name>.debug-assertions`
 746 * Type: boolean
 747 * Default: See profile docs.
 748 * Environment: `CARGO_PROFILE_<name>_DEBUG_ASSERTIONS`
 749
 750 See [debug-assertions](profiles.md#debug-assertions).
 751
 752 ##### `profile.<name>.incremental`
 753 * Type: boolean
 754 * Default: See profile docs.
 755 * Environment: `CARGO_PROFILE_<name>_INCREMENTAL`
 756
 757 See [incremental](profiles.md#incremental).
 758
 759 ##### `profile.<name>.lto`
 760 * Type: string or boolean
 761 * Default: See profile docs.
 762 * Environment: `CARGO_PROFILE_<name>_LTO`
 763
 764 See [lto](profiles.md#lto).
 765
 766 ##### `profile.<name>.overflow-checks`
 767 * Type: boolean
 768 * Default: See profile docs.
 769 * Environment: `CARGO_PROFILE_<name>_OVERFLOW_CHECKS`
 770
 771 See [overflow-checks](profiles.md#overflow-checks).
 772
 773 ##### `profile.<name>.opt-level`
 774 * Type: integer or string
 775 * Default: See profile docs.
 776 * Environment: `CARGO_PROFILE_<name>_OPT_LEVEL`
 777
 778 See [opt-level](profiles.md#opt-level).
 779
 780 ##### `profile.<name>.panic`
 781 * Type: string
 782 * default: See profile docs.
 783 * Environment: `CARGO_PROFILE_<name>_PANIC`
 784
 785 See [panic](profiles.md#panic).
 786
 787 ##### `profile.<name>.rpath`
 788 * Type: boolean
 789 * default: See profile docs.
 790 * Environment: `CARGO_PROFILE_<name>_RPATH`
 791
 792 See [rpath](profiles.md#rpath).
 793
 794
 795 #### `[registries]`
 796
 797 The `[registries]` table is used for specifying additional [registries]. It
 798 consists of a sub-table for each named registry.
 799
 800 ##### `registries.<name>.index`
 801 * Type: string (url)
 802 * Default: none
 803 * Environment: `CARGO_REGISTRIES_<name>_INDEX`
 804
 805 Specifies the URL of the git index for the registry.
 806
 807 ##### `registries.<name>.token`
 808 * Type: string
 809 * Default: none
 810 * Environment: `CARGO_REGISTRIES_<name>_TOKEN`
 811
 812 Specifies the authentication token for the given registry. This value should
 813 only appear in the [credentials](#credentials) file. This is used for registry
 814 commands like [`cargo publish`] that require authentication.
 815
 816 Can be overridden with the `--token` command-line option.
 817
 818 #### `[registry]`
 819
 820 The `[registry]` table controls the default registry used when one is not
 821 specified.
 822
 823 ##### `registry.index`
 824
 825 This value is no longer accepted and should not be used.
 826
 827 ##### `registry.default`
 828 * Type: string
 829 * Default: `"crates-io"`
 830 * Environment: `CARGO_REGISTRY_DEFAULT`
 831
 832 The name of the registry (from the [`registries` table](#registries)) to use
 833 by default for registry commands like [`cargo publish`].
 834
 835 Can be overridden with the `--registry` command-line option.
 836
 837 ##### `registry.token`
 838 * Type: string
 839 * Default: none
 840 * Environment: `CARGO_REGISTRY_TOKEN`
 841
 842 Specifies the authentication token for [crates.io]. This value should only
 843 appear in the [credentials](#credentials) file. This is used for registry
 844 commands like [`cargo publish`] that require authentication.
 845
 846 Can be overridden with the `--token` command-line option.
 847
 848 #### `[source]`
 849
 850 The `[source]` table defines the registry sources available. See [Source
 851 Replacement] for more information. It consists of a sub-table for each named
 852 source. A source should only define one kind (directory, registry,
 853 local-registry, or git).
 854
 855 ##### `source.<name>.replace-with`
 856 * Type: string
 857 * Default: none
 858 * Environment: not supported
 859
 860 If set, replace this source with the given named source.
 861
 862 ##### `source.<name>.directory`
 863 * Type: string (path)
 864 * Default: none
 865 * Environment: not supported
 866
 867 Sets the path to a directory to use as a directory source.
 868
 869 ##### `source.<name>.registry`
 870 * Type: string (url)
 871 * Default: none
 872 * Environment: not supported
 873
 874 Sets the URL to use for a registry source.
 875
 876 ##### `source.<name>.local-registry`
 877 * Type: string (path)
 878 * Default: none
 879 * Environment: not supported
 880
 881 Sets the path to a directory to use as a local registry source.
 882
 883 ##### `source.<name>.git`
 884 * Type: string (url)
 885 * Default: none
 886 * Environment: not supported
 887
 888 Sets the URL to use for a git repository source.
 889
 890 ##### `source.<name>.branch`
 891 * Type: string
 892 * Default: none
 893 * Environment: not supported
 894
 895 Sets the branch name to use for a git repository.
 896
 897 If none of `branch`, `tag`, or `rev` is set, defaults to the `master` branch.
 898
 899 ##### `source.<name>.tag`
 900 * Type: string
 901 * Default: none
 902 * Environment: not supported
 903
 904 Sets the tag name to use for a git repository.
 905
 906 If none of `branch`, `tag`, or `rev` is set, defaults to the `master` branch.
 907
 908 ##### `source.<name>.rev`
 909 * Type: string
 910 * Default: none
 911 * Environment: not supported
 912
 913 Sets the [revision] to use for a git repository.
 914
 915 If none of `branch`, `tag`, or `rev` is set, defaults to the `master` branch.
 916
 917
 918 #### `[target]`
 919
 920 The `[target]` table is used for specifying settings for specific platform
 921 targets. It consists of a sub-table which is either a platform triple or a
 922 [`cfg()` expression]. The given values will be used if the target platform
 923 matches either the `<triple>` value or the `<cfg>` expression.
 924
 925 ```toml
 926 [target.thumbv7m-none-eabi]
 927 linker = "arm-none-eabi-gcc"
 928 runner = "my-emulator"
 929 rustflags = ["…", "…"]
 930
 931 [target.'cfg(all(target_arch = "arm", target_os = "none"))']
 932 runner = "my-arm-wrapper"
 933 rustflags = ["…", "…"]
 934 ```
 935
 936 `cfg` values come from those built-in to the compiler (run `rustc --print=cfg`
 937 to view), values set by [build scripts], and extra `--cfg` flags passed to
 938 `rustc` (such as those defined in `RUSTFLAGS`). Do not try to match on
 939 `debug_assertions` or Cargo features like `feature="foo"`.
 940
 941 If using a target spec JSON file, the `<triple>` value is the filename stem.
 942 For example `--target foo/bar.json` would match `[target.bar]`.
 943
 944 ##### `target.<triple>.ar`
 945
 946 This option is deprecated and unused.
 947
 948 ##### `target.<triple>.linker`
 949 * Type: string (program path)
 950 * Default: none
 951 * Environment: `CARGO_TARGET_<triple>_LINKER`
 952
 953 Specifies the linker which is passed to `rustc` (via [`-C linker`]) when the
 954 `<triple>` is being compiled for. By default, the linker is not overridden.
 955
 956 ##### `target.<triple>.runner`
 957 * Type: string or array of strings ([program path and args])
 958 * Default: none
 959 * Environment: `CARGO_TARGET_<triple>_RUNNER`
 960
 961 If a runner is provided, executables for the target `<triple>` will be
 962 executed by invoking the specified runner with the actual executable passed as
 963 an argument. This applies to [`cargo run`], [`cargo test`] and [`cargo bench`]
 964 commands. By default, compiled executables are executed directly.
 965
 966 ##### `target.<cfg>.runner`
 967
 968 This is similar to the [target runner](#targettriplerunner), but using
 969 a [`cfg()` expression]. If both a `<triple>` and `<cfg>` runner match,
 970 the `<triple>` will take precedence. It is an error if more than one
 971 `<cfg>` runner matches the current target.
 972
 973 ##### `target.<triple>.rustflags`
 974 * Type: string or array of strings
 975 * Default: none
 976 * Environment: `CARGO_TARGET_<triple>_RUSTFLAGS`
 977
 978 Passes a set of custom flags to the compiler for this `<triple>`. The value
 979 may be a array of strings or a space-separated string.
 980
 981 See [`build.rustflags`](#buildrustflags) for more details on the different
 982 ways to specific extra flags.
 983
 984 ##### `target.<cfg>.rustflags`
 985
 986 This is similar to the [target rustflags](#targettriplerustflags), but
 987 using a [`cfg()` expression]. If several `<cfg>` and `<triple>` entries
 988 match the current target, the flags are joined together.
 989
 990 ##### `target.<triple>.<links>`
 991
 992 The links sub-table provides a way to [override a build script]. When
 993 specified, the build script for the given `links` library will not be
 994 run, and the given values will be used instead.
 995
 996 ```toml
 997 [target.x86_64-unknown-linux-gnu.foo]
 998 rustc-link-lib = ["foo"]
 999 rustc-link-search = ["/path/to/foo"]
1000 rustc-flags = "-L /some/path"
1001 rustc-cfg = ['key="value"']
1002 rustc-env = {key = "value"}
1003 rustc-cdylib-link-arg = ["…"]
1004 metadata_key1 = "value"
1005 metadata_key2 = "value"
1006 ```
1007
1008 #### `[term]`
1009
1010 The `[term]` table controls terminal output and interaction.
1011
1012 ##### `term.verbose`
1013 * Type: boolean
1014 * Default: false
1015 * Environment: `CARGO_TERM_VERBOSE`
1016
1017 Controls whether or not extra detailed messages are displayed by Cargo.
1018
1019 Specifying the `--quiet` flag will override and disable verbose output.
1020 Specifying the `--verbose` flag will override and force verbose output.
1021
1022 ##### `term.color`
1023 * Type: string
1024 * Default: "auto"
1025 * Environment: `CARGO_TERM_COLOR`
1026
1027 Controls whether or not colored output is used in the terminal. Possible values:
1028
1029 * `auto` (default): Automatically detect if color support is available on the
1030   terminal.
1031 * `always`: Always display colors.
1032 * `never`: Never display colors.
1033
1034 Can be overridden with the `--color` command-line option.
1035
1036 ##### `term.progress.when`
1037 * Type: string
1038 * Default: "auto"
1039 * Environment: `CARGO_TERM_PROGRESS_WHEN`
1040
1041 Controls whether or not progress bar is shown in the terminal. Possible values:
1042
1043 * `auto` (default): Intelligently guess whether to show progress bar.
1044 * `always`: Always show progress bar.
1045 * `never`: Never show progress bar.
1046
1047 ##### `term.progress.width`
1048 * Type: integer
1049 * Default: none
1050 * Environment: `CARGO_TERM_PROGRESS_WIDTH`
1051
1052 Sets the width for progress bar.
1053
1054 [`cargo bench`]: ../commands/cargo-bench.md
1055 [`cargo login`]: ../commands/cargo-login.md
1056 [`cargo doc`]: ../commands/cargo-doc.md
1057 [`cargo new`]: ../commands/cargo-new.md
1058 [`cargo publish`]: ../commands/cargo-publish.md
1059 [`cargo run`]: ../commands/cargo-run.md
1060 [`cargo rustc`]: ../commands/cargo-rustc.md
1061 [`cargo test`]: ../commands/cargo-test.md
1062 [`cargo rustdoc`]: ../commands/cargo-rustdoc.md
1063 [`cargo install`]: ../commands/cargo-install.md
1064 [env]: environment-variables.md
1065 [`cfg()` expression]: ../../reference/conditional-compilation.html
1066 [build scripts]: build-scripts.md
1067 [`-C linker`]: ../../rustc/codegen-options/index.md#linker
1068 [override a build script]: build-scripts.md#overriding-build-scripts
1069 [toml]: https://toml.io/
1070 [incremental compilation]: profiles.md#incremental
1071 [profile]: profiles.md
1072 [program path with args]: #executable-paths-with-arguments
1073 [libcurl format]: https://ec.haxx.se/usingcurl-proxies.html
1074 [source replacement]: source-replacement.md
1075 [revision]: https://git-scm.com/docs/gitrevisions
1076 [registries]: registries.md
1077 [crates.io]: https://crates.io/