docs-v2/content/flux/v0/stdlib/strings/hasprefix.md

title	description	menu	weight
strings.hasPrefix() function	`strings.hasPrefix()` indicates if a string begins with a specified prefix.	flux_v0_ref name parent identifier strings.hasPrefix strings strings/hasPrefix	101

strings.hasPrefix() indicates if a string begins with a specified prefix.

Function type signature

(prefix: string, v: string) => bool

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

Parameters

v

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

prefix

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

Examples

Filter based on the presence of a prefix in a column value

import "sampledata"
import "strings"

sampledata.string()
    |> filter(fn: (r) => strings.hasPrefix(v: r._value, prefix: "smpl_5"))

{{< expand-wrapper >}} {{% expand "View example input and output" %}}

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	*tag	_value
2021-01-01T00:00:40Z	t1	smpl_5v3cce

_time	*tag	_value
2021-01-01T00:00:20Z	t2	smpl_5g7tz4

{{% /expand %}} {{< /expand-wrapper >}}