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
  77 [doc]
  78 browser = "chromium"          # browser to use with `cargo doc --open`,
  79                               # overrides the `BROWSER` environment variable
  80
  81 [env]
  82 # Set ENV_VAR_NAME=value for any process run by Cargo
  83 ENV_VAR_NAME = "value"
  84 # Set even if already present in environment
  85 ENV_VAR_NAME_2 = { value = "value", force = true }
  86 # Value is relative to .cargo directory containing `config.toml`, make absolute
  87 ENV_VAR_NAME_3 = { value = "relative/path", relative = true }
  88
  89 [future-incompat-report]
  90 frequency = 'always' # when to display a notification about a future incompat report
  91
  92 [cargo-new]
  93 vcs = "none"              # VCS to use ('git', 'hg', 'pijul', 'fossil', 'none')
  94
  95 [http]
  96 debug = false               # HTTP debugging
  97 proxy = "host:port"         # HTTP proxy in libcurl format
  98 ssl-version = "tlsv1.3"     # TLS version to use
  99 ssl-version.max = "tlsv1.3" # maximum TLS version
 100 ssl-version.min = "tlsv1.1" # minimum TLS version
 101 timeout = 30                # timeout for each HTTP request, in seconds
 102 low-speed-limit = 10        # network timeout threshold (bytes/sec)
 103 cainfo = "cert.pem"         # path to Certificate Authority (CA) bundle
 104 check-revoke = true         # check for SSL certificate revocation
 105 multiplexing = true         # HTTP/2 multiplexing
 106 user-agent = "…"            # the user-agent header
 107
 108 [install]
 109 root = "/some/path"         # `cargo install` destination directory
 110
 111 [net]
 112 retry = 2                   # network retries
 113 git-fetch-with-cli = true   # use the `git` executable for git operations
 114 offline = true              # do not access the network
 115
 116 [patch.<registry>]
 117 # Same keys as for [patch] in Cargo.toml
 118
 119 [profile.<name>]         # Modify profile settings via config.
 120 opt-level = 0            # Optimization level.
 121 debug = true             # Include debug info.
 122 split-debuginfo = '...'  # Debug info splitting behavior.
 123 debug-assertions = true  # Enables debug assertions.
 124 overflow-checks = true   # Enables runtime integer overflow checks.
 125 lto = false              # Sets link-time optimization.
 126 panic = 'unwind'         # The panic strategy.
 127 incremental = true       # Incremental compilation.
 128 codegen-units = 16       # Number of code generation units.
 129 rpath = false            # Sets the rpath linking option.
 130 [profile.<name>.build-override]  # Overrides build-script settings.
 131 # Same keys for a normal profile.
 132 [profile.<name>.package.<name>]  # Override profile for a package.
 133 # Same keys for a normal profile (minus `panic`, `lto`, and `rpath`).
 134
 135 [registries.<name>]  # registries other than crates.io
 136 index = "…"          # URL of the registry index
 137 token = "…"          # authentication token for the registry
 138
 139 [registry]
 140 default = "…"        # name of the default registry
 141 token = "…"          # authentication token for crates.io
 142
 143 [source.<name>]      # source definition and replacement
 144 replace-with = "…"   # replace this source with the given named source
 145 directory = "…"      # path to a directory source
 146 registry = "…"       # URL to a registry source
 147 local-registry = "…" # path to a local registry source
 148 git = "…"            # URL of a git repository source
 149 branch = "…"         # branch name for the git repository
 150 tag = "…"            # tag name for the git repository
 151 rev = "…"            # revision for the git repository
 152
 153 [target.<triple>]
 154 linker = "…"            # linker to use
 155 runner = "…"            # wrapper to run executables
 156 rustflags = ["…", "…"]  # custom flags for `rustc`
 157
 158 [target.<cfg>]
 159 runner = "…"            # wrapper to run executables
 160 rustflags = ["…", "…"]  # custom flags for `rustc`
 161
 162 [target.<triple>.<links>] # `links` build script override
 163 rustc-link-lib = ["foo"]
 164 rustc-link-search = ["/path/to/foo"]
 165 rustc-flags = ["-L", "/some/path"]
 166 rustc-cfg = ['key="value"']
 167 rustc-env = {key = "value"}
 168 rustc-cdylib-link-arg = ["…"]
 169 metadata_key1 = "value"
 170 metadata_key2 = "value"
 171
 172 [term]
 173 quiet = false          # whether cargo output is quiet
 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
 444 This option is deprecated and unused. Cargo always has pipelining enabled.
 445
 446 #### `[doc]`
 447
 448 The `[doc]` table defines options for the [`cargo doc`] command.
 449
 450 ##### `doc.browser`
 451
 452 * Type: string or array of strings ([program path and args])
 453 * Default: `BROWSER` environment variable, or, if that is missing,
 454   opening the link in a system specific way
 455
 456 This option sets the browser to be used by [`cargo doc`], overriding the
 457 `BROWSER` environment variable when opening documentation with the `--open`
 458 option.
 459
 460 #### `[cargo-new]`
 461
 462 The `[cargo-new]` table defines defaults for the [`cargo new`] command.
 463
 464 ##### `cargo-new.name`
 465
 466 This option is deprecated and unused.
 467
 468 ##### `cargo-new.email`
 469
 470 This option is deprecated and unused.
 471
 472 ##### `cargo-new.vcs`
 473 * Type: string
 474 * Default: "git" or "none"
 475 * Environment: `CARGO_CARGO_NEW_VCS`
 476
 477 Specifies the source control system to use for initializing a new repository.
 478 Valid values are `git`, `hg` (for Mercurial), `pijul`, `fossil` or `none` to
 479 disable this behavior. Defaults to `git`, or `none` if already inside a VCS
 480 repository. Can be overridden with the `--vcs` CLI option.
 481
 482 ### `[env]`
 483
 484 The `[env]` section allows you to set additional environment variables for
 485 build scripts, rustc invocations, `cargo run` and `cargo build`.
 486
 487 ```toml
 488 [env]
 489 OPENSSL_DIR = "/opt/openssl"
 490 ```
 491
 492 By default, the variables specified will not override values that already exist
 493 in the environment. This behavior can be changed by setting the `force` flag.
 494
 495 Setting the `relative` flag evaluates the value as a config-relative path that
 496 is relative to the parent directory of the `.cargo` directory that contains the
 497 `config.toml` file. The value of the environment variable will be the full
 498 absolute path.
 499
 500 ```toml
 501 [env]
 502 TMPDIR = { value = "/home/tmp", force = true }
 503 OPENSSL_DIR = { value = "vendor/openssl", relative = true }
 504 ```
 505
 506 ### `[future-incompat-report]`
 507
 508 The `[future-incompat-report]` table controls setting for [future incompat reporting](future-incompat-report.md)
 509
 510 #### `future-incompat-report.frequency`
 511 * Type: string
 512 * Default: "always"
 513 * Environment: `CARGO_FUTURE_INCOMPAT_REPORT_FREQUENCY`
 514
 515 Controls how often we display a notification to the terminal when a future incompat report is available. Possible values:
 516
 517 * `always` (default): Always display a notification when a command (e.g. `cargo build`) produces a future incompat report
 518 * `never`: Never display a notification
 519
 520 #### `[http]`
 521
 522 The `[http]` table defines settings for HTTP behavior. This includes fetching
 523 crate dependencies and accessing remote git repositories.
 524
 525 ##### `http.debug`
 526 * Type: boolean
 527 * Default: false
 528 * Environment: `CARGO_HTTP_DEBUG`
 529
 530 If `true`, enables debugging of HTTP requests. The debug information can be
 531 seen by setting the `CARGO_LOG=cargo::ops::registry=debug` environment
 532 variable (or use `trace` for even more information).
 533
 534 Be wary when posting logs from this output in a public location. The output
 535 may include headers with authentication tokens which you don't want to leak!
 536 Be sure to review logs before posting them.
 537
 538 ##### `http.proxy`
 539 * Type: string
 540 * Default: none
 541 * Environment: `CARGO_HTTP_PROXY` or `HTTPS_PROXY` or `https_proxy` or `http_proxy`
 542
 543 Sets an HTTP and HTTPS proxy to use. The format is in [libcurl format] as in
 544 `[protocol://]host[:port]`. If not set, Cargo will also check the `http.proxy`
 545 setting in your global git configuration. If none of those are set, the
 546 `HTTPS_PROXY` or `https_proxy` environment variables set the proxy for HTTPS
 547 requests, and `http_proxy` sets it for HTTP requests.
 548
 549 ##### `http.timeout`
 550 * Type: integer
 551 * Default: 30
 552 * Environment: `CARGO_HTTP_TIMEOUT` or `HTTP_TIMEOUT`
 553
 554 Sets the timeout for each HTTP request, in seconds.
 555
 556 ##### `http.cainfo`
 557 * Type: string (path)
 558 * Default: none
 559 * Environment: `CARGO_HTTP_CAINFO`
 560
 561 Path to a Certificate Authority (CA) bundle file, used to verify TLS
 562 certificates. If not specified, Cargo attempts to use the system certificates.
 563
 564 ##### `http.check-revoke`
 565 * Type: boolean
 566 * Default: true (Windows) false (all others)
 567 * Environment: `CARGO_HTTP_CHECK_REVOKE`
 568
 569 This determines whether or not TLS certificate revocation checks should be
 570 performed. This only works on Windows.
 571
 572 ##### `http.ssl-version`
 573 * Type: string or min/max table
 574 * Default: none
 575 * Environment: `CARGO_HTTP_SSL_VERSION`
 576
 577 This sets the minimum TLS version to use. It takes a string, with one of the
 578 possible values of "default", "tlsv1", "tlsv1.0", "tlsv1.1", "tlsv1.2", or
 579 "tlsv1.3".
 580
 581 This may alternatively take a table with two keys, `min` and `max`, which each
 582 take a string value of the same kind that specifies the minimum and maximum
 583 range of TLS versions to use.
 584
 585 The default is a minimum version of "tlsv1.0" and a max of the newest version
 586 supported on your platform, typically "tlsv1.3".
 587
 588 ##### `http.low-speed-limit`
 589 * Type: integer
 590 * Default: 10
 591 * Environment: `CARGO_HTTP_LOW_SPEED_LIMIT`
 592
 593 This setting controls timeout behavior for slow connections. If the average
 594 transfer speed in bytes per second is below the given value for
 595 [`http.timeout`](#httptimeout) seconds (default 30 seconds), then the
 596 connection is considered too slow and Cargo will abort and retry.
 597
 598 ##### `http.multiplexing`
 599 * Type: boolean
 600 * Default: true
 601 * Environment: `CARGO_HTTP_MULTIPLEXING`
 602
 603 When `true`, Cargo will attempt to use the HTTP2 protocol with multiplexing.
 604 This allows multiple requests to use the same connection, usually improving
 605 performance when fetching multiple files. If `false`, Cargo will use HTTP 1.1
 606 without pipelining.
 607
 608 ##### `http.user-agent`
 609 * Type: string
 610 * Default: Cargo's version
 611 * Environment: `CARGO_HTTP_USER_AGENT`
 612
 613 Specifies a custom user-agent header to use. The default if not specified is a
 614 string that includes Cargo's version.
 615
 616 #### `[install]`
 617
 618 The `[install]` table defines defaults for the [`cargo install`] command.
 619
 620 ##### `install.root`
 621 * Type: string (path)
 622 * Default: Cargo's home directory
 623 * Environment: `CARGO_INSTALL_ROOT`
 624
 625 Sets the path to the root directory for installing executables for [`cargo
 626 install`]. Executables go into a `bin` directory underneath the root.
 627
 628 To track information of installed executables, some extra files, such as
 629 `.crates.toml` and `.crates2.json`, are also created under this root.
 630
 631 The default if not specified is Cargo's home directory (default `.cargo` in
 632 your home directory).
 633
 634 Can be overridden with the `--root` command-line option.
 635
 636 #### `[net]`
 637
 638 The `[net]` table controls networking configuration.
 639
 640 ##### `net.retry`
 641 * Type: integer
 642 * Default: 2
 643 * Environment: `CARGO_NET_RETRY`
 644
 645 Number of times to retry possibly spurious network errors.
 646
 647 ##### `net.git-fetch-with-cli`
 648 * Type: boolean
 649 * Default: false
 650 * Environment: `CARGO_NET_GIT_FETCH_WITH_CLI`
 651
 652 If this is `true`, then Cargo will use the `git` executable to fetch registry
 653 indexes and git dependencies. If `false`, then it uses a built-in `git`
 654 library.
 655
 656 Setting this to `true` can be helpful if you have special authentication
 657 requirements that Cargo does not support. See [Git
 658 Authentication](../appendix/git-authentication.md) for more information about
 659 setting up git authentication.
 660
 661 ##### `net.offline`
 662 * Type: boolean
 663 * Default: false
 664 * Environment: `CARGO_NET_OFFLINE`
 665
 666 If this is `true`, then Cargo will avoid accessing the network, and attempt to
 667 proceed with locally cached data. If `false`, Cargo will access the network as
 668 needed, and generate an error if it encounters a network error.
 669
 670 Can be overridden with the `--offline` command-line option.
 671
 672 #### `[patch]`
 673
 674 Just as you can override dependencies using [`[patch]` in
 675 `Cargo.toml`](overriding-dependencies.md#the-patch-section), you can
 676 override them in the cargo configuration file to apply those patches to
 677 any affected build. The format is identical to the one used in
 678 `Cargo.toml`.
 679
 680 Since `.cargo/config.toml` files are not usually checked into source
 681 control, you should prefer patching using `Cargo.toml` where possible to
 682 ensure that other developers can compile your crate in their own
 683 environments. Patching through cargo configuration files is generally
 684 only appropriate when the patch section is automatically generated by an
 685 external build tool.
 686
 687 If a given dependency is patched both in a cargo configuration file and
 688 a `Cargo.toml` file, the patch in the configuration file is used. If
 689 multiple configuration files patch the same dependency, standard cargo
 690 configuration merging is used, which prefers the value defined closest
 691 to the current directory, with `$HOME/.cargo/config.toml` taking the
 692 lowest precedence.
 693
 694 Relative `path` dependencies in such a `[patch]` section are resolved
 695 relative to the configuration file they appear in.
 696
 697 #### `[profile]`
 698
 699 The `[profile]` table can be used to globally change profile settings, and
 700 override settings specified in `Cargo.toml`. It has the same syntax and
 701 options as profiles specified in `Cargo.toml`. See the [Profiles chapter] for
 702 details about the options.
 703
 704 [Profiles chapter]: profiles.md
 705
 706 ##### `[profile.<name>.build-override]`
 707 * Environment: `CARGO_PROFILE_<name>_BUILD_OVERRIDE_<key>`
 708
 709 The build-override table overrides settings for build scripts, proc macros,
 710 and their dependencies. It has the same keys as a normal profile. See the
 711 [overrides section](profiles.md#overrides) for more details.
 712
 713 ##### `[profile.<name>.package.<name>]`
 714 * Environment: not supported
 715
 716 The package table overrides settings for specific packages. It has the same
 717 keys as a normal profile, minus the `panic`, `lto`, and `rpath` settings. See
 718 the [overrides section](profiles.md#overrides) for more details.
 719
 720 ##### `profile.<name>.codegen-units`
 721 * Type: integer
 722 * Default: See profile docs.
 723 * Environment: `CARGO_PROFILE_<name>_CODEGEN_UNITS`
 724
 725 See [codegen-units](profiles.md#codegen-units).
 726
 727 ##### `profile.<name>.debug`
 728 * Type: integer or boolean
 729 * Default: See profile docs.
 730 * Environment: `CARGO_PROFILE_<name>_DEBUG`
 731
 732 See [debug](profiles.md#debug).
 733
 734 ##### `profile.<name>.split-debuginfo`
 735 * Type: string
 736 * Default: See profile docs.
 737 * Environment: `CARGO_PROFILE_<name>_SPLIT_DEBUGINFO`
 738
 739 See [split-debuginfo](profiles.md#split-debuginfo).
 740
 741 ##### `profile.<name>.debug-assertions`
 742 * Type: boolean
 743 * Default: See profile docs.
 744 * Environment: `CARGO_PROFILE_<name>_DEBUG_ASSERTIONS`
 745
 746 See [debug-assertions](profiles.md#debug-assertions).
 747
 748 ##### `profile.<name>.incremental`
 749 * Type: boolean
 750 * Default: See profile docs.
 751 * Environment: `CARGO_PROFILE_<name>_INCREMENTAL`
 752
 753 See [incremental](profiles.md#incremental).
 754
 755 ##### `profile.<name>.lto`
 756 * Type: string or boolean
 757 * Default: See profile docs.
 758 * Environment: `CARGO_PROFILE_<name>_LTO`
 759
 760 See [lto](profiles.md#lto).
 761
 762 ##### `profile.<name>.overflow-checks`
 763 * Type: boolean
 764 * Default: See profile docs.
 765 * Environment: `CARGO_PROFILE_<name>_OVERFLOW_CHECKS`
 766
 767 See [overflow-checks](profiles.md#overflow-checks).
 768
 769 ##### `profile.<name>.opt-level`
 770 * Type: integer or string
 771 * Default: See profile docs.
 772 * Environment: `CARGO_PROFILE_<name>_OPT_LEVEL`
 773
 774 See [opt-level](profiles.md#opt-level).
 775
 776 ##### `profile.<name>.panic`
 777 * Type: string
 778 * default: See profile docs.
 779 * Environment: `CARGO_PROFILE_<name>_PANIC`
 780
 781 See [panic](profiles.md#panic).
 782
 783 ##### `profile.<name>.rpath`
 784 * Type: boolean
 785 * default: See profile docs.
 786 * Environment: `CARGO_PROFILE_<name>_RPATH`
 787
 788 See [rpath](profiles.md#rpath).
 789
 790
 791 #### `[registries]`
 792
 793 The `[registries]` table is used for specifying additional [registries]. It
 794 consists of a sub-table for each named registry.
 795
 796 ##### `registries.<name>.index`
 797 * Type: string (url)
 798 * Default: none
 799 * Environment: `CARGO_REGISTRIES_<name>_INDEX`
 800
 801 Specifies the URL of the git index for the registry.
 802
 803 ##### `registries.<name>.token`
 804 * Type: string
 805 * Default: none
 806 * Environment: `CARGO_REGISTRIES_<name>_TOKEN`
 807
 808 Specifies the authentication token for the given registry. This value should
 809 only appear in the [credentials](#credentials) file. This is used for registry
 810 commands like [`cargo publish`] that require authentication.
 811
 812 Can be overridden with the `--token` command-line option.
 813
 814 #### `[registry]`
 815
 816 The `[registry]` table controls the default registry used when one is not
 817 specified.
 818
 819 ##### `registry.index`
 820
 821 This value is no longer accepted and should not be used.
 822
 823 ##### `registry.default`
 824 * Type: string
 825 * Default: `"crates-io"`
 826 * Environment: `CARGO_REGISTRY_DEFAULT`
 827
 828 The name of the registry (from the [`registries` table](#registries)) to use
 829 by default for registry commands like [`cargo publish`].
 830
 831 Can be overridden with the `--registry` command-line option.
 832
 833 ##### `registry.token`
 834 * Type: string
 835 * Default: none
 836 * Environment: `CARGO_REGISTRY_TOKEN`
 837
 838 Specifies the authentication token for [crates.io]. This value should only
 839 appear in the [credentials](#credentials) file. This is used for registry
 840 commands like [`cargo publish`] that require authentication.
 841
 842 Can be overridden with the `--token` command-line option.
 843
 844 #### `[source]`
 845
 846 The `[source]` table defines the registry sources available. See [Source
 847 Replacement] for more information. It consists of a sub-table for each named
 848 source. A source should only define one kind (directory, registry,
 849 local-registry, or git).
 850
 851 ##### `source.<name>.replace-with`
 852 * Type: string
 853 * Default: none
 854 * Environment: not supported
 855
 856 If set, replace this source with the given named source.
 857
 858 ##### `source.<name>.directory`
 859 * Type: string (path)
 860 * Default: none
 861 * Environment: not supported
 862
 863 Sets the path to a directory to use as a directory source.
 864
 865 ##### `source.<name>.registry`
 866 * Type: string (url)
 867 * Default: none
 868 * Environment: not supported
 869
 870 Sets the URL to use for a registry source.
 871
 872 ##### `source.<name>.local-registry`
 873 * Type: string (path)
 874 * Default: none
 875 * Environment: not supported
 876
 877 Sets the path to a directory to use as a local registry source.
 878
 879 ##### `source.<name>.git`
 880 * Type: string (url)
 881 * Default: none
 882 * Environment: not supported
 883
 884 Sets the URL to use for a git repository source.
 885
 886 ##### `source.<name>.branch`
 887 * Type: string
 888 * Default: none
 889 * Environment: not supported
 890
 891 Sets the branch name to use for a git repository.
 892
 893 If none of `branch`, `tag`, or `rev` is set, defaults to the `master` branch.
 894
 895 ##### `source.<name>.tag`
 896 * Type: string
 897 * Default: none
 898 * Environment: not supported
 899
 900 Sets the tag name to use for a git repository.
 901
 902 If none of `branch`, `tag`, or `rev` is set, defaults to the `master` branch.
 903
 904 ##### `source.<name>.rev`
 905 * Type: string
 906 * Default: none
 907 * Environment: not supported
 908
 909 Sets the [revision] to use for a git repository.
 910
 911 If none of `branch`, `tag`, or `rev` is set, defaults to the `master` branch.
 912
 913
 914 #### `[target]`
 915
 916 The `[target]` table is used for specifying settings for specific platform
 917 targets. It consists of a sub-table which is either a platform triple or a
 918 [`cfg()` expression]. The given values will be used if the target platform
 919 matches either the `<triple>` value or the `<cfg>` expression.
 920
 921 ```toml
 922 [target.thumbv7m-none-eabi]
 923 linker = "arm-none-eabi-gcc"
 924 runner = "my-emulator"
 925 rustflags = ["…", "…"]
 926
 927 [target.'cfg(all(target_arch = "arm", target_os = "none"))']
 928 runner = "my-arm-wrapper"
 929 rustflags = ["…", "…"]
 930 ```
 931
 932 `cfg` values come from those built-in to the compiler (run `rustc --print=cfg`
 933 to view), values set by [build scripts], and extra `--cfg` flags passed to
 934 `rustc` (such as those defined in `RUSTFLAGS`). Do not try to match on
 935 `debug_assertions` or Cargo features like `feature="foo"`.
 936
 937 If using a target spec JSON file, the `<triple>` value is the filename stem.
 938 For example `--target foo/bar.json` would match `[target.bar]`.
 939
 940 ##### `target.<triple>.ar`
 941
 942 This option is deprecated and unused.
 943
 944 ##### `target.<triple>.linker`
 945 * Type: string (program path)
 946 * Default: none
 947 * Environment: `CARGO_TARGET_<triple>_LINKER`
 948
 949 Specifies the linker which is passed to `rustc` (via [`-C linker`]) when the
 950 `<triple>` is being compiled for. By default, the linker is not overridden.
 951
 952 ##### `target.<triple>.runner`
 953 * Type: string or array of strings ([program path and args])
 954 * Default: none
 955 * Environment: `CARGO_TARGET_<triple>_RUNNER`
 956
 957 If a runner is provided, executables for the target `<triple>` will be
 958 executed by invoking the specified runner with the actual executable passed as
 959 an argument. This applies to [`cargo run`], [`cargo test`] and [`cargo bench`]
 960 commands. By default, compiled executables are executed directly.
 961
 962 ##### `target.<cfg>.runner`
 963
 964 This is similar to the [target runner](#targettriplerunner), but using
 965 a [`cfg()` expression]. If both a `<triple>` and `<cfg>` runner match,
 966 the `<triple>` will take precedence. It is an error if more than one
 967 `<cfg>` runner matches the current target.
 968
 969 ##### `target.<triple>.rustflags`
 970 * Type: string or array of strings
 971 * Default: none
 972 * Environment: `CARGO_TARGET_<triple>_RUSTFLAGS`
 973
 974 Passes a set of custom flags to the compiler for this `<triple>`. The value
 975 may be a array of strings or a space-separated string.
 976
 977 See [`build.rustflags`](#buildrustflags) for more details on the different
 978 ways to specific extra flags.
 979
 980 ##### `target.<cfg>.rustflags`
 981
 982 This is similar to the [target rustflags](#targettriplerustflags), but
 983 using a [`cfg()` expression]. If several `<cfg>` and `<triple>` entries
 984 match the current target, the flags are joined together.
 985
 986 ##### `target.<triple>.<links>`
 987
 988 The links sub-table provides a way to [override a build script]. When
 989 specified, the build script for the given `links` library will not be
 990 run, and the given values will be used instead.
 991
 992 ```toml
 993 [target.x86_64-unknown-linux-gnu.foo]
 994 rustc-link-lib = ["foo"]
 995 rustc-link-search = ["/path/to/foo"]
 996 rustc-flags = "-L /some/path"
 997 rustc-cfg = ['key="value"']
 998 rustc-env = {key = "value"}
 999 rustc-cdylib-link-arg = ["…"]
1000 metadata_key1 = "value"
1001 metadata_key2 = "value"
1002 ```
1003
1004 #### `[term]`
1005
1006 The `[term]` table controls terminal output and interaction.
1007
1008 ##### `term.quiet`
1009 * Type: boolean
1010 * Default: false
1011 * Environment: `CARGO_TERM_QUIET`
1012
1013 Controls whether or not log messages are displayed by Cargo.
1014
1015 Specifying the `--quiet` flag will override and force quiet output.
1016 Specifying the `--verbose` flag will override and disable quiet output.
1017
1018 ##### `term.verbose`
1019 * Type: boolean
1020 * Default: false
1021 * Environment: `CARGO_TERM_VERBOSE`
1022
1023 Controls whether or not extra detailed messages are displayed by Cargo.
1024
1025 Specifying the `--quiet` flag will override and disable verbose output.
1026 Specifying the `--verbose` flag will override and force verbose output.
1027
1028 ##### `term.color`
1029 * Type: string
1030 * Default: "auto"
1031 * Environment: `CARGO_TERM_COLOR`
1032
1033 Controls whether or not colored output is used in the terminal. Possible values:
1034
1035 * `auto` (default): Automatically detect if color support is available on the
1036   terminal.
1037 * `always`: Always display colors.
1038 * `never`: Never display colors.
1039
1040 Can be overridden with the `--color` command-line option.
1041
1042 ##### `term.progress.when`
1043 * Type: string
1044 * Default: "auto"
1045 * Environment: `CARGO_TERM_PROGRESS_WHEN`
1046
1047 Controls whether or not progress bar is shown in the terminal. Possible values:
1048
1049 * `auto` (default): Intelligently guess whether to show progress bar.
1050 * `always`: Always show progress bar.
1051 * `never`: Never show progress bar.
1052
1053 ##### `term.progress.width`
1054 * Type: integer
1055 * Default: none
1056 * Environment: `CARGO_TERM_PROGRESS_WIDTH`
1057
1058 Sets the width for progress bar.
1059
1060 [`cargo bench`]: ../commands/cargo-bench.md
1061 [`cargo login`]: ../commands/cargo-login.md
1062 [`cargo doc`]: ../commands/cargo-doc.md
1063 [`cargo new`]: ../commands/cargo-new.md
1064 [`cargo publish`]: ../commands/cargo-publish.md
1065 [`cargo run`]: ../commands/cargo-run.md
1066 [`cargo rustc`]: ../commands/cargo-rustc.md
1067 [`cargo test`]: ../commands/cargo-test.md
1068 [`cargo rustdoc`]: ../commands/cargo-rustdoc.md
1069 [`cargo install`]: ../commands/cargo-install.md
1070 [env]: environment-variables.md
1071 [`cfg()` expression]: ../../reference/conditional-compilation.html
1072 [build scripts]: build-scripts.md
1073 [`-C linker`]: ../../rustc/codegen-options/index.md#linker
1074 [override a build script]: build-scripts.md#overriding-build-scripts
1075 [toml]: https://toml.io/
1076 [incremental compilation]: profiles.md#incremental
1077 [profile]: profiles.md
1078 [program path with args]: #executable-paths-with-arguments
1079 [libcurl format]: https://ec.haxx.se/usingcurl-proxies.html
1080 [source replacement]: source-replacement.md
1081 [revision]: https://git-scm.com/docs/gitrevisions
1082 [registries]: registries.md
1083 [crates.io]: https://crates.io/