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Documentation: Explain --config.expand-env=true double slash with slash substitution #6139

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May 31, 2022
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Documentation: Explain --config.expand-env=true double slash with slash substitution #6139

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66f69ac
docs: Promtail configuration explain expand-env slash pitfall
V-Mann-Nick May 10, 2022
4d37e77
docs: link to correct envsubst go package
V-Mann-Nick May 19, 2022
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5 changes: 5 additions & 0 deletions docs/sources/clients/promtail/configuration.md
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Expand Up @@ -60,6 +60,11 @@ ${VAR:default_value}

Where default_value is the value to use if the environment variable is undefined.

**Note**: With `expand-env=true` the configuration will first run through
[envsubst](https://linux.die.net/man/1/envsubst) which will replace double
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slashes with single slashes. Because of this every use of a slash `\` needs to
be replaced with a double slash `\\`

### Generic placeholders:

- `<boolean>`: a boolean that can take the values `true` or `false`
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10 changes: 10 additions & 0 deletions docs/sources/clients/promtail/stages/regex.md
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Expand Up @@ -38,6 +38,16 @@ But these are not:
- `expression: '\\w*'` (only escape backslashes when using double quotes)
- `expression: "\w*"` (backslash must be escaped)


If you run Promtail with the `--config.expand-env=true` flag the configuration
will run through [envsubst](https://linux.die.net/man/1/envsubst) which will
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replace double slashes with single slashes. Because of this when using
`expand-env=true` you need to use double slashes for each single slash. For
example:

- `expression: '\w*'` must be `expression: '\\w*'`
- `expression: "\\w*"` must be `expression: "\\\\w*"`

## Example

### Without `source`
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