docs-v2/content/flux/v0.x/stdlib/strings/index-fn.md

title	description	menu	weight
strings.index() function	`strings.index()` returns the index of the first instance of a substring in a string. If the substring is not present, it returns `-1`.	flux_0_x_ref name parent identifier strings.index strings strings/index	101

strings.index() returns the index of the first instance of a substring in a string. If the substring is not present, it returns -1.

Function type signature

(substr: string, v: string) => int

{{% caption %}}For more information, see Function type signatures.{{% /caption %}}

Parameters

v

({{< req >}}) String value to search.

substr

({{< req >}}) Substring to search for.

Examples

Find the index of the first occurrence of a substring

import "sampledata"
import "strings"

sampledata.string()
    |> map(fn: (r) => ({r with _value: strings.index(v: r._value, substr: "g")}))

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Input data

_time	*tag	_value
2021-01-01T00:00:00Z	t1	smpl_g9qczs
2021-01-01T00:00:10Z	t1	smpl_0mgv9n
2021-01-01T00:00:20Z	t1	smpl_phw664
2021-01-01T00:00:30Z	t1	smpl_guvzy4
2021-01-01T00:00:40Z	t1	smpl_5v3cce
2021-01-01T00:00:50Z	t1	smpl_s9fmgy

_time	*tag	_value
2021-01-01T00:00:00Z	t2	smpl_b5eida
2021-01-01T00:00:10Z	t2	smpl_eu4oxp
2021-01-01T00:00:20Z	t2	smpl_5g7tz4
2021-01-01T00:00:30Z	t2	smpl_sox1ut
2021-01-01T00:00:40Z	t2	smpl_wfm757
2021-01-01T00:00:50Z	t2	smpl_dtn2bv

Output data

_time	_value	*tag
2021-01-01T00:00:00Z	5	t1
2021-01-01T00:00:10Z	7	t1
2021-01-01T00:00:20Z	-1	t1
2021-01-01T00:00:30Z	5	t1
2021-01-01T00:00:40Z	-1	t1
2021-01-01T00:00:50Z	9	t1

_time	_value	*tag
2021-01-01T00:00:00Z	-1	t2
2021-01-01T00:00:10Z	-1	t2
2021-01-01T00:00:20Z	6	t2
2021-01-01T00:00:30Z	-1	t2
2021-01-01T00:00:40Z	-1	t2
2021-01-01T00:00:50Z	-1	t2

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