docs: env: bash-style default value operator :-#2568
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📝 WalkthroughWalkthroughClarifies Fluent Bit environment-variable substitution: lists supported syntaxes including ChangesEnvironment Variable Substitution Documentation
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Actionable comments posted: 1
🧹 Nitpick comments (2)
administration/configuring-fluent-bit/classic-mode/variables.md (2)
22-26: 💤 Low valueMinor terminology clarification.
The phrase "primary variable" at line 23 could be simplified to just "the variable" for clarity. The word "primary" doesn't add meaningful distinction here since there's only one variable being evaluated.
📝 Proposed simplification
-If the `${VARIABLE:-DEFAULT}` syntax is used, Fluent Bit will use the `DEFAULT` value if the primary variable meets either of the following conditions: +If the `${VARIABLE:-DEFAULT}` syntax is used, Fluent Bit will use the `DEFAULT` value if the variable meets either of the following conditions:🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the rest with a brief reason, keep changes minimal, and validate. In `@administration/configuring-fluent-bit/classic-mode/variables.md` around lines 22 - 26, Replace the phrase "primary variable" with "the variable" in the "Fallback Behavior" section describing the `${VARIABLE:-DEFAULT}` syntax so the bullet points read that Fluent Bit will use the `DEFAULT` value if the variable is not defined (unset) or is defined but set to an empty string; update the sentence containing "primary variable" under the "Fallback Behavior" heading to use "the variable" for clarity.
17-17: 💤 Low valueGrammar: Use hyphen to join compound modifier.
"Debian based system" should be "Debian-based system" when used as a compound adjective before a noun.
📝 Proposed fix
-- `/etc/default/fluent-bit` (Debian based system) +- `/etc/default/fluent-bit` (Debian-based system)🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the rest with a brief reason, keep changes minimal, and validate. In `@administration/configuring-fluent-bit/classic-mode/variables.md` at line 17, The phrase "/etc/default/fluent-bit (Debian based system)" uses "Debian based" as a compound modifier; update that text to read "/etc/default/fluent-bit (Debian-based system)" so the compound adjective is hyphenated correctly.
🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
Inline comments:
In `@administration/configuring-fluent-bit/yaml/environment-variables-section.md`:
- Around line 68-79: The "Default Values" section currently says defaults apply
only "if the variable is not defined"; update the text to state that the
`${VARIABLE_NAME:-DEFAULT_VALUE}` syntax supplies the DEFAULT_VALUE both when
the variable is unset and when it is defined but set to an empty string, so the
behavior matches the classic-mode doc; adjust the explanatory sentence and any
examples (the `service.flush: ${FLUSH_INTERVAL:-5}` example) to reflect this
dual-case behavior and ensure wording mirrors the classic-mode variables.md
description.
---
Nitpick comments:
In `@administration/configuring-fluent-bit/classic-mode/variables.md`:
- Around line 22-26: Replace the phrase "primary variable" with "the variable"
in the "Fallback Behavior" section describing the `${VARIABLE:-DEFAULT}` syntax
so the bullet points read that Fluent Bit will use the `DEFAULT` value if the
variable is not defined (unset) or is defined but set to an empty string; update
the sentence containing "primary variable" under the "Fallback Behavior" heading
to use "the variable" for clarity.
- Line 17: The phrase "/etc/default/fluent-bit (Debian based system)" uses
"Debian based" as a compound modifier; update that text to read
"/etc/default/fluent-bit (Debian-based system)" so the compound adjective is
hyphenated correctly.
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I don't believe this is correct, the variable defaulting syntax is inherent to the shell itself rather than the config file.
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@benjaminmueggenburg-serato my review requires some fixes first.
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🧹 Nitpick comments (1)
administration/configuring-fluent-bit/classic-mode/variables.md (1)
23-23: 💤 Low valueConsider simplifying "primary variable" to "variable".
The term "primary variable" is slightly awkward since there's no secondary variable being discussed. Simply "variable" would be more direct.
📝 Suggested simplification
-If the `${VARIABLE:-DEFAULT}` syntax is used, Fluent Bit will use the `DEFAULT` value if the primary variable meets either of the following conditions: +If the `${VARIABLE:-DEFAULT}` syntax is used, Fluent Bit will use the `DEFAULT` value if the variable meets either of the following conditions:🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the rest with a brief reason, keep changes minimal, and validate. In `@administration/configuring-fluent-bit/classic-mode/variables.md` at line 23, The sentence describing `${VARIABLE:-DEFAULT}` should use "variable" instead of the awkward phrase "primary variable"; update the text "if the primary variable meets either of the following conditions" to "if the variable meets either of the following conditions" so the wording is simpler and clearer (refer to the existing `${VARIABLE:-DEFAULT}` example in the same sentence).
🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
Nitpick comments:
In `@administration/configuring-fluent-bit/classic-mode/variables.md`:
- Line 23: The sentence describing `${VARIABLE:-DEFAULT}` should use "variable"
instead of the awkward phrase "primary variable"; update the text "if the
primary variable meets either of the following conditions" to "if the variable
meets either of the following conditions" so the wording is simpler and clearer
(refer to the existing `${VARIABLE:-DEFAULT}` example in the same sentence).
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administration/configuring-fluent-bit/classic-mode/variables.mdadministration/configuring-fluent-bit/yaml/environment-variables-section.md
✅ Files skipped from review due to trivial changes (1)
- administration/configuring-fluent-bit/yaml/environment-variables-section.md
patrick-stephens
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Implementation is merged now so just waiting on a release.
We may need to flag the minimum version this feature is supported in as well, i.e. it is >5.0.4.
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Signed-off-by: benjaminmueggenburg-serato <benjamin.mueggenburg@serato.com>
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cosmo0920
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May 15, 2026
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FYI: This feature will be shipped as v5.0.6 not v5.0.5. |
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Small change requested!
| 1. The variable **isn't defined** (unset). | ||
| 2. The variable is defined but set to an **empty string** (`''`). | ||
|
|
||
| Nesting **isn't supported**. You cannot use the `${}` syntax within another `${}` definition. `${MY_VAR:-${OTHER_VAR}}` would be invalid. |
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@benjaminmueggenburg-serato small fix needed here for vale lint issue.
Signed-off-by: Eric D. Schabell <eric@schabell.org>
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Fixed listing for you @benjaminmueggenburg-serato so we can get this in the docs for 5.0.6. |
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🧹 Nitpick comments (2)
administration/configuring-fluent-bit/classic-mode/variables.md (2)
9-10: 💤 Low valueConsider consistent placeholder naming across examples.
Line 10 uses
default_valuewhile line 27 usesDEFAULTas the placeholder. For reader clarity, consider using the same placeholder style throughout the document.📝 Suggested adjustment for consistency
-* **With Default Value:** `${MY_VARIABLE:-default_value}` (**v5.0.6+**) +* **With Default Value:** `${MY_VARIABLE:-default}` (**v5.0.6+**)🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the rest with a brief reason, keep changes minimal, and validate. In `@administration/configuring-fluent-bit/classic-mode/variables.md` around lines 9 - 10, Replace the inconsistent placeholder between examples so all examples use the same placeholder style; specifically, make `${MY_VARIABLE:-default_value}` match the other example that currently uses `${MY_VARIABLE:-DEFAULT}` by changing the latter to `${MY_VARIABLE:-default_value}` (or vice versa) so `${MY_VARIABLE}` and the defaulted form use a consistent placeholder naming throughout the document.
21-31: ⚡ Quick winExpand contractions for technical documentation standards.
Vale linters commonly flag contractions in technical documentation. The following contractions should be expanded:
- Line 28: "isn't defined" → "is not defined"
- Line 31: "isn't supported" → "is not supported"
- Line 31: "can't use" → "cannot use"
📝 Proposed fix
-1. The variable **isn't defined** (unset). +1. The variable **is not defined** (unset). 2. The variable is defined but set to an **empty string** (`''`). -Nesting **isn't supported**. You can't use the `${}` syntax within another `${}` definition. `${MY_VAR:-${OTHER_VAR}}` would be invalid. +Nesting **is not supported**. You cannot use the `${}` syntax within another `${}` definition. `${MY_VAR:-${OTHER_VAR}}` would be invalid.🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the rest with a brief reason, keep changes minimal, and validate. In `@administration/configuring-fluent-bit/classic-mode/variables.md` around lines 21 - 31, Update the text surrounding the `${VARIABLE:-DEFAULT}` section to expand contractions: replace "isn't defined" with "is not defined" in the sentence describing when DEFAULT is used, and replace "isn't supported" with "is not supported" and "can't use" with "cannot use" in the sentence about nesting; keep the examples and the `${MY_VAR:-${OTHER_VAR}}` invalid-example intact and preserve formatting and hint block.
🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
Nitpick comments:
In `@administration/configuring-fluent-bit/classic-mode/variables.md`:
- Around line 9-10: Replace the inconsistent placeholder between examples so all
examples use the same placeholder style; specifically, make
`${MY_VARIABLE:-default_value}` match the other example that currently uses
`${MY_VARIABLE:-DEFAULT}` by changing the latter to
`${MY_VARIABLE:-default_value}` (or vice versa) so `${MY_VARIABLE}` and the
defaulted form use a consistent placeholder naming throughout the document.
- Around line 21-31: Update the text surrounding the `${VARIABLE:-DEFAULT}`
section to expand contractions: replace "isn't defined" with "is not defined" in
the sentence describing when DEFAULT is used, and replace "isn't supported" with
"is not supported" and "can't use" with "cannot use" in the sentence about
nesting; keep the examples and the `${MY_VAR:-${OTHER_VAR}}` invalid-example
intact and preserve formatting and hint block.
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📒 Files selected for processing (2)
administration/configuring-fluent-bit/classic-mode/variables.mdadministration/configuring-fluent-bit/yaml/environment-variables-section.md
✅ Files skipped from review due to trivial changes (1)
- administration/configuring-fluent-bit/yaml/environment-variables-section.md
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Waiting on code merge: fluent/fluent-bit#11787
Updates documentation to mention the default value operator i.e
${ENV_VAR:-default}. Feature applies to both legacy config and YAML config files.Has some examples, and details the expected behaviour.
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