mirror of https://github.com/grafana/loki
Add function label_replace. (#3047)
You might be wondering why do we need label_replace when we already have label_format. Well for two reasons: 1. It's nice to have something similar to Prometheus, so users building metric queries will feel right at home. 2. Interestingly, they are quite different in how they execute. label_format executes for every log line, however label_replace execute for every sample. Since you aggregate log lines into sample then label_replace is way more efficient at scale. Signed-off-by: Cyril Tovena <cyril.tovena@gmail.com>pull/3053/head^2
Cyril Tovena
5 years ago
committed by
GitHub
parent
4e7a123c77
commit
3f0800dc44
@ -1,370 +1,15 @@ |
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--- |
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title: Template functions |
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title: Functions |
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--- |
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|
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The [text template](https://golang.org/pkg/text/template) format used in `| line_format` and `| label_format` support the usage of functions. |
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# Functions |
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|
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All labels are added as variables in the template engine. They can be referenced using they label name prefixed by a `.`(e.g `.label_name`). For example the following template will output the value of the path label: |
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## label_replace() |
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|
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```template |
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{{ .path }} |
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``` |
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|
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You can take advantage of [pipeline](https://golang.org/pkg/text/template/#hdr-Pipelines) to join together multiple functions. |
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In a chained pipeline, the result of each command is passed as the last argument of the following command. |
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|
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Example: |
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|
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```template |
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{{ .path | replace " " "_" | trunc 5 | upper }} |
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``` |
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|
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## ToLower and ToUpper |
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This function converts the entire string to lowercase or uppercase. |
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|
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Signatures: |
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- `ToLower(string) string` |
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- `ToUpper(string) string` |
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|
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Examples: |
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|
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```template |
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"{{.request_method | ToLower}}" |
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"{{.request_method | ToUpper}}" |
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`{{ToUpper "This is a string" | ToLower}}` |
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``` |
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|
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> **Note:** In Loki 2.1 you can also use respectively [`lower`](#lower) and [`upper`](#upper) shortcut, e.g `{{.request_method | lower }}`. |
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|
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## Replace string |
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|
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> **Note:** In Loki 2.1 [`replace`](#replace) (as opposed to `Replace`) is available with a different signature but easier to chain within pipeline. |
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|
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Use this function to perform a simple string replacement. |
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|
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Signature: |
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|
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`Replace(s, old, new string, n int) string` |
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|
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It takes four arguments: |
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|
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- `s` source string |
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- `old` string to replace |
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- `new` string to replace with |
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- `n` the maximun amount of replacement (-1 for all) |
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|
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Example: |
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|
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```template |
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`{{ Replace "This is a string" " " "-" -1 }}` |
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``` |
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|
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The results in `This-is-a-string`. |
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|
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## Trim, TrimLeft, TrimRight, and TrimSpace |
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|
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> **Note:** In Loki 2.1 [trim](#trim), [trimAll](#trimAll), [trimSuffix](#trimSuffix) and [trimPrefix](trimPrefix) have been added with a different signature for better pipeline chaining. |
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|
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`Trim` returns a slice of the string s with all leading and |
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trailing Unicode code points contained in cutset removed. |
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|
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Signature: `Trim(value, cutset string) string` |
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|
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`TrimLeft` and `TrimRight` are the same as `Trim` except that it trims only leading and trailing characters respectively. |
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|
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```template |
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`{{ Trim .query ",. " }}` |
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`{{ TrimLeft .uri ":" }}` |
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`{{ TrimRight .path "/" }}` |
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``` |
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|
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`TrimSpace` TrimSpace returns string s with all leading |
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and trailing white space removed, as defined by Unicode. |
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|
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Signature: `TrimSpace(value string) string` |
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|
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```template |
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{{ TrimSpace .latency }} |
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``` |
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|
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`TrimPrefix` and `TrimSuffix` will trim respectively the prefix or suffix supplied. |
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|
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Signature: |
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- `TrimPrefix(value string, prefix string) string` |
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- `TrimSuffix(value string, suffix string) string` |
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|
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```template |
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{{ TrimPrefix .path "/" }} |
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``` |
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|
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## regexReplaceAll and regexReplaceAllLiteral |
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|
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`regexReplaceAll` returns a copy of the input string, replacing matches of the Regexp with the replacement string replacement. Inside string replacement, $ signs are interpreted as in Expand, so for instance $1 represents the text of the first sub-match. See the golang [Regexp.replaceAll documentation](https://golang.org/pkg/regexp/#Regexp.ReplaceAll) for more examples. |
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|
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```template |
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`{{ regexReplaceAllLiteral "(a*)bc" .some_label "${1}a" }}` |
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``` |
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|
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`regexReplaceAllLiteral` function returns a copy of the input string and replaces matches of the Regexp with the replacement string replacement. The replacement string is substituted directly, without using Expand. |
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|
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```template |
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`{{ regexReplaceAllLiteral "(ts=)" .timestamp "timestamp=" }}` |
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``` |
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|
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You can combine multiple functions using pipe. For example, to strip out spaces and make the request method in capital, you would write the following template: `{{ .request_method | TrimSpace | ToUpper }}`. |
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|
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## lower |
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> Added in Loki 2.1 |
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Use this function to convert to lower case. |
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Signature: |
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`lower(string) string` |
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Examples: |
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|
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```template |
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"{{ .request_method | lower }}" |
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`{{ lower "HELLO"}}` |
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``` |
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The last example will return `hello`. |
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|
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## upper |
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> Added in Loki 2.1 |
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|
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Use this function to convert to upper case. |
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|
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Signature: |
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|
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`upper(string) string` |
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|
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Examples: |
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|
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```template |
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"{{ .request_method | upper }}" |
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`{{ upper "hello"}}` |
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``` |
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This results in `HELLO`. |
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|
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## title |
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> **Note:** Added in Loki 2.1. |
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Convert to title case. |
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Signature: |
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`title(string) string` |
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|
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Examples: |
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|
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```template |
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"{{.request_method | title}}" |
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`{{ title "hello world"}}` |
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``` |
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The last example will return `Hello World`. |
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|
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## trunc |
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> **Note:** Added in Loki 2.1. |
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Truncate a string and add no suffix. |
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Signature: |
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`trunc(count int,value string) string` |
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Examples: |
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```template |
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"{{ .path | trunc 2 }}" |
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`{{ trunc 5 "hello world"}}` // output: hello |
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`{{ trunc -5 "hello world"}}` // output: world |
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``` |
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|
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## substr |
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> **Note:** Added in Loki 2.1. |
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Get a substring from a string. |
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Signature: |
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`trunc(start int,end int,value string) string` |
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If start is < 0, this calls value[:end]. |
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If start is >= 0 and end < 0 or end bigger than s length, this calls value[start:] |
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Otherwise, this calls value[start, end]. |
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Examples: |
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```template |
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"{{ .path | substr 2 5 }}" |
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`{{ substr 0 5 "hello world"}}` // output: hello |
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`{{ substr 6 11 "hello world"}}` // output: world |
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``` |
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## replace |
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> **Note:** Added in Loki 2.1. |
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This function performs simple string replacement. |
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Signature: `replace(old string, new string, src string) string` |
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It takes three arguments: |
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- `old` string to replace |
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- `new` string to replace with |
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- `src` source string |
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Examples: |
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```template |
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{{ .cluster | replace "-cluster" "" }} |
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{{ replace "hello" "world" "hello world" }} |
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``` |
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The last example will return `world world`. |
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## trim |
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> **Note:** Added in Loki 2.1. |
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The trim function removes space from either side of a string. |
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Signature: `trim(string) string` |
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Examples: |
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```template |
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{{ .ip | trim }} |
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{{ trim " hello " }} // output: hello |
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``` |
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## trimAll |
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> **Note:** Added in Loki 2.1. |
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Use this function to remove given characters from the front or back of a string. |
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Signature: `trimAll(chars string,src string) string` |
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Examples: |
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```template |
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{{ .path | trimAll "/" }} |
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{{ trimAll "$" "$5.00" }} // output: 5.00 |
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``` |
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## trimSuffix |
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> **Note:** Added in Loki 2.1. |
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Use this function to trim just the suffix from a string. |
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Signature: `trimSuffix(suffix string, src string) string` |
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Examples: |
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```template |
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{{ .path | trimSuffix "/" }} |
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{{ trimSuffix "-" "hello-" }} // output: hello |
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``` |
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## trimPrefix |
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> **Note:** Added in Loki 2.1. |
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Use this function to trim just the prefix from a string. |
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Signature: `trimPrefix(suffix string, src string) string` |
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Examples: |
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```template |
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{{ .path | trimPrefix "/" }} |
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{{ trimPrefix "-" "-hello" }} // output: hello |
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``` |
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## indent |
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> **Note:** Added in Loki 2.1. |
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The indent function indents every line in a given string to the specified indent width. This is useful when aligning multi-line strings. |
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Signature: `indent(spaces int,src string) string` |
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```template |
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{{ indent 4 .query }} |
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``` |
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This indents each line contained in the `.query` by four (4) spaces. |
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## nindent |
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> **Note:** Added in Loki 2.1. |
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The nindent function is the same as the indent function, but prepends a new line to the beginning of the string. |
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Signature: `nindent(spaces int,src string) string` |
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```template |
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{{ nindent 4 .query }} |
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``` |
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This will indent every line of text by 4 space characters and add a new line to the beginning. |
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## repeat |
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> **Note:** Added in Loki 2.1. |
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Use this function to repeat a string multiple times. |
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Signature: `repeat(c int,value string) string` |
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```template |
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{{ repeat 3 "hello" }} // output: hellohellohello |
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``` |
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## contains |
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> **Note:** Added in Loki 2.1. |
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Use this function to test to see if one string is contained inside of another. |
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Signature: `contains(s string, src string) bool` |
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Examples: |
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```template |
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{{ if .err contains "ErrTimeout" }} timeout {{end}} |
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{{ if contains "he" "hello" }} yes {{end}} |
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``` |
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## hasPrefix and hasSuffix |
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> **Note:** Added in Loki 2.1. |
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The `hasPrefix` and `hasSuffix` functions test whether a string has a given prefix or suffix. |
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Signatures: |
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- `hasPrefix(prefix string, src string) bool` |
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- `hasSuffix(suffix string, src string) bool` |
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For each timeseries in `v`, `label_replace(v instant-vector, dst_label string, replacement string, src_label string, regex string)` matches the regular expression `regex` against the label `src_label`. If it matches, then the timeseries is returned with the label `dst_label` replaced by the expansion of `replacement`. `$1` is replaced with the first matching subgroup, `$2` with the second etc. If the regular expression doesn't match then the timeseries is returned unchanged. |
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Examples: |
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This example will return a vector with each time series having a `foo` label with the value `a` added to it: |
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|
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```template |
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{{ if .err hasSuffix "Timeout" }} timeout {{end}} |
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{{ if hasPrefix "he" "hello" }} yes {{end}} |
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```logql |
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label_replace(rate({job="api-server",service="a:c"} |= "err" [1m]), "foo", "$1", "service", "(.*):.*") |
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``` |
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@ -0,0 +1,373 @@ |
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--- |
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title: Template functions |
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--- |
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# Template functions |
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|
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The [text template](https://golang.org/pkg/text/template) format used in `| line_format` and `| label_format` support the usage of functions. |
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All labels are added as variables in the template engine. They can be referenced using they label name prefixed by a `.`(e.g `.label_name`). For example the following template will output the value of the path label: |
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```template |
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{{ .path }} |
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``` |
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You can take advantage of [pipeline](https://golang.org/pkg/text/template/#hdr-Pipelines) to join together multiple functions. |
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In a chained pipeline, the result of each command is passed as the last argument of the following command. |
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|
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Example: |
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```template |
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{{ .path | replace " " "_" | trunc 5 | upper }} |
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``` |
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## ToLower and ToUpper |
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This function converts the entire string to lowercase or uppercase. |
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Signatures: |
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- `ToLower(string) string` |
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- `ToUpper(string) string` |
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|
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Examples: |
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|
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```template |
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"{{.request_method | ToLower}}" |
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"{{.request_method | ToUpper}}" |
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`{{ToUpper "This is a string" | ToLower}}` |
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``` |
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|
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> **Note:** In Loki 2.1 you can also use respectively [`lower`](#lower) and [`upper`](#upper) shortcut, e.g `{{.request_method | lower }}`. |
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## Replace string |
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|
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> **Note:** In Loki 2.1 [`replace`](#replace) (as opposed to `Replace`) is available with a different signature but easier to chain within pipeline. |
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Use this function to perform a simple string replacement. |
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Signature: |
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`Replace(s, old, new string, n int) string` |
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It takes four arguments: |
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|
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- `s` source string |
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- `old` string to replace |
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- `new` string to replace with |
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- `n` the maximun amount of replacement (-1 for all) |
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|
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Example: |
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```template |
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`{{ Replace "This is a string" " " "-" -1 }}` |
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``` |
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The results in `This-is-a-string`. |
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## Trim, TrimLeft, TrimRight, and TrimSpace |
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|
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> **Note:** In Loki 2.1 [trim](#trim), [trimAll](#trimAll), [trimSuffix](#trimSuffix) and [trimPrefix](trimPrefix) have been added with a different signature for better pipeline chaining. |
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|
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`Trim` returns a slice of the string s with all leading and |
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trailing Unicode code points contained in cutset removed. |
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Signature: `Trim(value, cutset string) string` |
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`TrimLeft` and `TrimRight` are the same as `Trim` except that it trims only leading and trailing characters respectively. |
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|
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```template |
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`{{ Trim .query ",. " }}` |
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`{{ TrimLeft .uri ":" }}` |
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`{{ TrimRight .path "/" }}` |
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``` |
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`TrimSpace` TrimSpace returns string s with all leading |
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and trailing white space removed, as defined by Unicode. |
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Signature: `TrimSpace(value string) string` |
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```template |
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{{ TrimSpace .latency }} |
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``` |
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`TrimPrefix` and `TrimSuffix` will trim respectively the prefix or suffix supplied. |
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Signature: |
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- `TrimPrefix(value string, prefix string) string` |
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- `TrimSuffix(value string, suffix string) string` |
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```template |
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{{ TrimPrefix .path "/" }} |
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``` |
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## regexReplaceAll and regexReplaceAllLiteral |
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`regexReplaceAll` returns a copy of the input string, replacing matches of the Regexp with the replacement string replacement. Inside string replacement, $ signs are interpreted as in Expand, so for instance $1 represents the text of the first sub-match. See the golang [Regexp.replaceAll documentation](https://golang.org/pkg/regexp/#Regexp.ReplaceAll) for more examples. |
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|
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```template |
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`{{ regexReplaceAllLiteral "(a*)bc" .some_label "${1}a" }}` |
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``` |
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`regexReplaceAllLiteral` function returns a copy of the input string and replaces matches of the Regexp with the replacement string replacement. The replacement string is substituted directly, without using Expand. |
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|
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```template |
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`{{ regexReplaceAllLiteral "(ts=)" .timestamp "timestamp=" }}` |
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``` |
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|
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You can combine multiple functions using pipe. For example, to strip out spaces and make the request method in capital, you would write the following template: `{{ .request_method | TrimSpace | ToUpper }}`. |
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|
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## lower |
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|
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> Added in Loki 2.1 |
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|
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Use this function to convert to lower case. |
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|
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Signature: |
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|
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`lower(string) string` |
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|
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Examples: |
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|
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```template |
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"{{ .request_method | lower }}" |
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`{{ lower "HELLO"}}` |
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``` |
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The last example will return `hello`. |
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|
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## upper |
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|
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> Added in Loki 2.1 |
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|
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Use this function to convert to upper case. |
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|
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Signature: |
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|
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`upper(string) string` |
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|
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Examples: |
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|
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```template |
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"{{ .request_method | upper }}" |
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`{{ upper "hello"}}` |
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``` |
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This results in `HELLO`. |
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|
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## title |
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|
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> **Note:** Added in Loki 2.1. |
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|
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Convert to title case. |
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|
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Signature: |
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|
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`title(string) string` |
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|
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Examples: |
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|
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```template |
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"{{.request_method | title}}" |
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`{{ title "hello world"}}` |
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``` |
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The last example will return `Hello World`. |
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|
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## trunc |
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|
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> **Note:** Added in Loki 2.1. |
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|
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Truncate a string and add no suffix. |
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|
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Signature: |
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|
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`trunc(count int,value string) string` |
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|
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Examples: |
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|
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```template |
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"{{ .path | trunc 2 }}" |
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`{{ trunc 5 "hello world"}}` // output: hello |
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`{{ trunc -5 "hello world"}}` // output: world |
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``` |
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|
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## substr |
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|
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> **Note:** Added in Loki 2.1. |
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|
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Get a substring from a string. |
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|
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Signature: |
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|
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`trunc(start int,end int,value string) string` |
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|
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If start is < 0, this calls value[:end]. |
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If start is >= 0 and end < 0 or end bigger than s length, this calls value[start:] |
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Otherwise, this calls value[start, end]. |
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|
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Examples: |
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|
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```template |
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"{{ .path | substr 2 5 }}" |
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`{{ substr 0 5 "hello world"}}` // output: hello |
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`{{ substr 6 11 "hello world"}}` // output: world |
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``` |
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|
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## replace |
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|
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> **Note:** Added in Loki 2.1. |
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|
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This function performs simple string replacement. |
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|
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Signature: `replace(old string, new string, src string) string` |
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|
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It takes three arguments: |
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|
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- `old` string to replace |
||||
- `new` string to replace with |
||||
- `src` source string |
||||
|
||||
Examples: |
||||
|
||||
```template |
||||
{{ .cluster | replace "-cluster" "" }} |
||||
{{ replace "hello" "world" "hello world" }} |
||||
``` |
||||
|
||||
The last example will return `world world`. |
||||
|
||||
## trim |
||||
|
||||
> **Note:** Added in Loki 2.1. |
||||
|
||||
The trim function removes space from either side of a string. |
||||
|
||||
Signature: `trim(string) string` |
||||
|
||||
Examples: |
||||
|
||||
```template |
||||
{{ .ip | trim }} |
||||
{{ trim " hello " }} // output: hello |
||||
``` |
||||
|
||||
## trimAll |
||||
|
||||
> **Note:** Added in Loki 2.1. |
||||
|
||||
Use this function to remove given characters from the front or back of a string. |
||||
|
||||
Signature: `trimAll(chars string,src string) string` |
||||
|
||||
Examples: |
||||
|
||||
```template |
||||
{{ .path | trimAll "/" }} |
||||
{{ trimAll "$" "$5.00" }} // output: 5.00 |
||||
``` |
||||
|
||||
## trimSuffix |
||||
|
||||
> **Note:** Added in Loki 2.1. |
||||
|
||||
Use this function to trim just the suffix from a string. |
||||
|
||||
Signature: `trimSuffix(suffix string, src string) string` |
||||
|
||||
Examples: |
||||
|
||||
```template |
||||
{{ .path | trimSuffix "/" }} |
||||
{{ trimSuffix "-" "hello-" }} // output: hello |
||||
``` |
||||
|
||||
## trimPrefix |
||||
|
||||
> **Note:** Added in Loki 2.1. |
||||
|
||||
Use this function to trim just the prefix from a string. |
||||
|
||||
Signature: `trimPrefix(suffix string, src string) string` |
||||
|
||||
Examples: |
||||
|
||||
```template |
||||
{{ .path | trimPrefix "/" }} |
||||
{{ trimPrefix "-" "-hello" }} // output: hello |
||||
``` |
||||
|
||||
## indent |
||||
|
||||
> **Note:** Added in Loki 2.1. |
||||
|
||||
The indent function indents every line in a given string to the specified indent width. This is useful when aligning multi-line strings. |
||||
|
||||
Signature: `indent(spaces int,src string) string` |
||||
|
||||
```template |
||||
{{ indent 4 .query }} |
||||
``` |
||||
|
||||
This indents each line contained in the `.query` by four (4) spaces. |
||||
|
||||
## nindent |
||||
|
||||
> **Note:** Added in Loki 2.1. |
||||
|
||||
The nindent function is the same as the indent function, but prepends a new line to the beginning of the string. |
||||
|
||||
Signature: `nindent(spaces int,src string) string` |
||||
|
||||
```template |
||||
{{ nindent 4 .query }} |
||||
``` |
||||
|
||||
This will indent every line of text by 4 space characters and add a new line to the beginning. |
||||
|
||||
## repeat |
||||
|
||||
> **Note:** Added in Loki 2.1. |
||||
|
||||
Use this function to repeat a string multiple times. |
||||
|
||||
Signature: `repeat(c int,value string) string` |
||||
|
||||
```template |
||||
{{ repeat 3 "hello" }} // output: hellohellohello |
||||
``` |
||||
|
||||
## contains |
||||
|
||||
> **Note:** Added in Loki 2.1. |
||||
|
||||
Use this function to test to see if one string is contained inside of another. |
||||
|
||||
Signature: `contains(s string, src string) bool` |
||||
|
||||
Examples: |
||||
|
||||
```template |
||||
{{ if .err contains "ErrTimeout" }} timeout {{end}} |
||||
{{ if contains "he" "hello" }} yes {{end}} |
||||
``` |
||||
|
||||
## hasPrefix and hasSuffix |
||||
|
||||
> **Note:** Added in Loki 2.1. |
||||
|
||||
The `hasPrefix` and `hasSuffix` functions test whether a string has a given prefix or suffix. |
||||
|
||||
Signatures: |
||||
|
||||
- `hasPrefix(prefix string, src string) bool` |
||||
- `hasSuffix(suffix string, src string) bool` |
||||
|
||||
Examples: |
||||
|
||||
```template |
||||
{{ if .err hasSuffix "Timeout" }} timeout {{end}} |
||||
{{ if hasPrefix "he" "hello" }} yes {{end}} |
||||
``` |
||||
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