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# substringBeforeLast

> Return the part of a string before the last occurrence of a specified substring.

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</section>

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<section class="usage">

## Usage

```javascript
var substringBeforeLast = require( '@stdlib/string/substring-before-last' );
```

#### substringBeforeLast( str, search )

Returns the part of a string before the last occurrence of a specified substring.

```javascript
var str = 'Beep Boop Beep';
var out = substringBeforeLast( str, 'Beep' );
// returns 'Beep Boop '

out = substringBeforeLast( str, 'Boop' );
// returns 'Beep '
```

</section>

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## Notes

-   If a substring is not present in a provided string, the function returns the input string.
-   If provided an empty substring, the function returns the input string.

</section>

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## Examples

<!-- eslint no-undef: "error" -->

```javascript
var substringBeforeLast = require( '@stdlib/string/substring-before-last' );

var str = 'beep boop';
var out = substringBeforeLast( str, ' ' );
// returns 'beep'

out = substringBeforeLast( str, 'e' );
// returns 'be'

out = substringBeforeLast( str, 'x' );
// returns 'beep boop'

out = substringBeforeLast( str, '' );
// returns 'beep boop'
```

</section>

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* * *

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## CLI

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### Usage

```text
Usage: substring-before-last [options] --search=<string> [<string>]

Options:

  -h,    --help                Print this message.
  -V,    --version             Print the package version.
         --search string       Search string.
         --split sep           Delimiter for stdin data. Default: '/\\r?\\n/'.
```

</section>

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### Notes

-   If the split separator is a [regular expression][mdn-regexp], ensure that the `split` option is either properly escaped or enclosed in quotes.

    ```bash
    # Not escaped...
    $ echo -n $'foo\nbar\nbaz' | substring-before-last --search a --split /\r?\n/

    # Escaped...
    $ echo -n $'foo\nbar\nbaz' | substring-before-last --search a --split /\\r?\\n/
    ```

-   The implementation ignores trailing delimiters.

</section>

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<section class="examples">

### Examples

```bash
$ substring-before-last abcdefg --search d
abc
```

To use as a [standard stream][standard-streams],

```bash
$ echo -n $'beep\nboop' | substring-before-last --search p
bee
boo
```

By default, when used as a [standard stream][standard-streams], the implementation assumes newline-delimited data. To specify an alternative delimiter, set the `split` option.

```bash
$ echo -n 'beep\tboop' | substring-before-last --search p --split '\t'
bee
boo
```

</section>

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</section>

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</section>

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* * *

## See Also

-   <span class="package-name">[`@stdlib/string/substring-before`][@stdlib/string/substring-before]</span><span class="delimiter">: </span><span class="description">return the part of a string before a specified substring.</span>
-   <span class="package-name">[`@stdlib/string/substring-after`][@stdlib/string/substring-after]</span><span class="delimiter">: </span><span class="description">return the part of a string after a specified substring.</span>
-   <span class="package-name">[`@stdlib/string/substring-after-last`][@stdlib/string/substring-after-last]</span><span class="delimiter">: </span><span class="description">return the part of a string after the last occurrence of a specified substring.</span>

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[standard-streams]: https://en.wikipedia.org/wiki/Standard_streams

[mdn-regexp]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions

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[@stdlib/string/substring-before]: https://github.com/stdlib-js/string/tree/main/substring-before

[@stdlib/string/substring-after]: https://github.com/stdlib-js/string/tree/main/substring-after

[@stdlib/string/substring-after-last]: https://github.com/stdlib-js/string/tree/main/substring-after-last

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</section>

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