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| 1 | +<!-- front-matter |
| 2 | +id: explaining-globs |
| 3 | +title: Explaining Globs |
| 4 | +hide_title: true |
| 5 | +sidebar_label: Explaining Globs |
| 6 | +--> |
| 7 | + |
| 8 | +# Explaining Globs |
| 9 | + |
| 10 | +A glob is a string of literal and/or wildcard characters used to match filepaths. Globbing is the act of locating files on a filesystem using one or more globs. |
| 11 | + |
| 12 | +The `src()` method expects a single glob string or an array of globs to determine which files your pipeline will operate on. At least one match must be found for your glob(s) otherwise `src()` will error. When an array of globs is used, they are matched in array order - especially useful for negative globs. |
| 13 | + |
| 14 | +## Segments and separators |
| 15 | + |
| 16 | +A segment is everything between separators. The separator in a glob is always the `/` character - regardless of the operating system - even in Windows where the path separator is `\\`. In a glob, `\\` is reserved as the escape character. |
| 17 | + |
| 18 | +Here, the * is escaped, so it is treated as a literal instead of a wildcard character. |
| 19 | +```js |
| 20 | +'glob_with_uncommon_\\*_character.js' |
| 21 | +``` |
| 22 | + |
| 23 | +Avoid using Node's `path` methods, like `path.join`, to create globs. On Windows, it produces an invalid glob because Node uses `\\` as the separator. Also avoid the `__dirname` global, `__filename` global, or `process.cwd()` for the same reasons. |
| 24 | + |
| 25 | +```js |
| 26 | +const invalidGlob = path.join(__dirname, 'src/*.js'); |
| 27 | +``` |
| 28 | + |
| 29 | +## Special character: * (single-star) |
| 30 | + |
| 31 | +Matches any amount - including none - of characters within a single segment. Useful for globbing files within one directory. |
| 32 | + |
| 33 | +This glob will match files like `index.js`, but not files like `scripts/index.js` or `scripts/nested/index.js` |
| 34 | +```js |
| 35 | +'*.js' |
| 36 | +``` |
| 37 | + |
| 38 | +## Special character: ** (double-star) |
| 39 | + |
| 40 | +Matches any amount - including none - of characters across segments. Useful for globbing files in nested directories. Make sure to appropriately restrict your double-star globs, to avoid matching large directories unnecessarily. |
| 41 | + |
| 42 | +Here, the glob is appropriately restricted to the `scripts/` directory. It will match files like `scripts/index.js`, `scripts/nested/index.js`, and `scripts/nested/twice/index.js`. |
| 43 | + |
| 44 | +```js |
| 45 | +'scripts/**/*.js' |
| 46 | +``` |
| 47 | + |
| 48 | +<small>In the previous example, if `scripts/` wasn't prefixed, all dependencies in `node_modules` or other directories would also be matched.</small> |
| 49 | + |
| 50 | +## Special character: ! (negative) |
| 51 | + |
| 52 | +Since globs are matched in array order, a negative glob must follow at least one non-negative glob in an array. The first finds a set of matches, then the negative glob removes a portion of those results. These are most performant when they only include literal characters. |
| 53 | + |
| 54 | +```js |
| 55 | +['script/**/*.js', '!scripts/vendor/'] |
| 56 | +``` |
| 57 | + |
| 58 | +If any non-negative globs follow a negative, nothing will be removed from the later set of matches. |
| 59 | + |
| 60 | +```js |
| 61 | +['script/**/*.js', '!scripts/vendor/', 'scripts/vendor/react.js'] |
| 62 | +``` |
| 63 | + |
| 64 | +Negative globs can be used as an alternative for restricting double-star globs. |
| 65 | + |
| 66 | +```js |
| 67 | +['**/*.js', '!node_modules/'] |
| 68 | +``` |
| 69 | + |
| 70 | +<small>In the previous example, if the negative glob was `!node_modules/**/*.js`, every match would have to be compared against the negative glob, which would be extremely slow.</small> |
| 71 | + |
| 72 | +## Overlapping globs |
| 73 | + |
| 74 | +Two or more globs that (un)intentionally match the same file are considered overlapping. When overlapping globs are used within a single `src()`, gulp does its best to remove the duplicates, but doesn't attempt to deduplicate across separate `src()` calls. |
| 75 | + |
| 76 | +## Advanced resources |
| 77 | + |
| 78 | +Most of what you'll need to work with globs in gulp is covered here. If you'd like to get more in depth, here are a few resources. |
| 79 | + |
| 80 | +* [Micromatch Documentation][micromatch-docs] |
| 81 | +* [node-glob's Glob Primer][glob-primer-docs] |
| 82 | +* [Begin's Globbing Documentation][begin-globbing-docs] |
| 83 | +* [Wikipedia's Glob Page][wikipedia-glob] |
| 84 | + |
| 85 | +[micromatch-docs]: https://github.com/micromatch/micromatch |
| 86 | +[glob-primer-docs]: https://github.com/isaacs/node-glob#glob-primer |
| 87 | +[begin-globbing-docs]: https://github.com/begin/globbing#what-is-globbing |
| 88 | +[wikipedia-glob]: https://en.wikipedia.org/wiki/Glob_(programming) |
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