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

title	description	menu	weight
strings.substring() function	`strings.substring()` returns a substring based on start and end parameters. These parameters are represent indices of UTF code points in the string.	flux_0_x_ref name parent identifier strings.substring strings strings/substring	101

strings.substring() returns a substring based on start and end parameters. These parameters are represent indices of UTF code points in the string.

When start or end are past the bounds of the string, respecitvely the start or end of the string is assumed. When end is less than or equal to start an empty string is returned.

Function type signature

(end: int, start: int, v: string) => string

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

Parameters

v

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

start

({{< req >}}) Starting inclusive index of the substring.

end

({{< req >}}) Ending exclusive index of the substring.

Examples

Return part of a string based on character index

import "sampledata"
import "strings"

sampledata.string()
    |> map(fn: (r) => ({r with _value: strings.substring(v: r._value, start: 5, end: 9)}))

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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	g9qc	t1
2021-01-01T00:00:10Z	0mgv	t1
2021-01-01T00:00:20Z	phw6	t1
2021-01-01T00:00:30Z	guvz	t1
2021-01-01T00:00:40Z	5v3c	t1
2021-01-01T00:00:50Z	s9fm	t1

_time	_value	*tag
2021-01-01T00:00:00Z	b5ei	t2
2021-01-01T00:00:10Z	eu4o	t2
2021-01-01T00:00:20Z	5g7t	t2
2021-01-01T00:00:30Z	sox1	t2
2021-01-01T00:00:40Z	wfm7	t2
2021-01-01T00:00:50Z	dtn2	t2

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