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lang/funcs: Type conversion functions It's not normally necessary to make explicit type conversions in Terraform because the language implicitly converts as necessary, but explicit conversions are useful in a few specialized cases: - When defining output values for a reusable module, it may be desirable to force a "cleaner" output type than would naturally arise from a computation, such as forcing a string containing digits into a number. - Our 0.12upgrade mechanism will use some of these to replace use of the undocumented, hidden type conversion functions in HIL, and force particular type interpretations in some tricky cases. - We've found that type conversion functions can be useful as _temporary_ workarounds for bugs in Terraform and in providers where implicit type conversion isn't working correctly or a type constraint isn't specified precisely enough for the automatic conversion behavior. These all follow the same convention of being named "to" followed by a short type name. Since we've had a long-standing convention of running all the words together in lowercase in function names, we stick to that here even though some of these names are quite strange, because these should be rarely-used functions anyway.
2019-01-17 18:11:48 +01:00
---
website: Adopt a ton of pages into the "language" layout As of this commit, that layout doesn't exist yet, but I'm isolating the one-line changes to their own commit to try and keep your eyes from glazing over.
2020-08-15 03:51:06 +02:00
layout: "language"
lang/funcs: Type conversion functions It's not normally necessary to make explicit type conversions in Terraform because the language implicitly converts as necessary, but explicit conversions are useful in a few specialized cases: - When defining output values for a reusable module, it may be desirable to force a "cleaner" output type than would naturally arise from a computation, such as forcing a string containing digits into a number. - Our 0.12upgrade mechanism will use some of these to replace use of the undocumented, hidden type conversion functions in HIL, and force particular type interpretations in some tricky cases. - We've found that type conversion functions can be useful as _temporary_ workarounds for bugs in Terraform and in providers where implicit type conversion isn't working correctly or a type constraint isn't specified precisely enough for the automatic conversion behavior. These all follow the same convention of being named "to" followed by a short type name. Since we've had a long-standing convention of running all the words together in lowercase in function names, we stick to that here even though some of these names are quite strange, because these should be rarely-used functions anyway.
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page_title: "tostring - Functions - Configuration Language"
sidebar_current: "docs-funcs-conversion-tostring"
description: |-
The tostring function converts a value to a string.
---
# `tostring` Function
website: Version notes: Add new -> old links to 0.12 language docs (function pages)
2019-01-17 01:33:57 +01:00
-> **Note:** This page is about Terraform 0.12 and later. For Terraform 0.11 and
earlier, see
[0.11 Configuration Language: Interpolation Syntax](../../configuration-0-11/interpolation.html).
lang/funcs: Type conversion functions It's not normally necessary to make explicit type conversions in Terraform because the language implicitly converts as necessary, but explicit conversions are useful in a few specialized cases: - When defining output values for a reusable module, it may be desirable to force a "cleaner" output type than would naturally arise from a computation, such as forcing a string containing digits into a number. - Our 0.12upgrade mechanism will use some of these to replace use of the undocumented, hidden type conversion functions in HIL, and force particular type interpretations in some tricky cases. - We've found that type conversion functions can be useful as _temporary_ workarounds for bugs in Terraform and in providers where implicit type conversion isn't working correctly or a type constraint isn't specified precisely enough for the automatic conversion behavior. These all follow the same convention of being named "to" followed by a short type name. Since we've had a long-standing convention of running all the words together in lowercase in function names, we stick to that here even though some of these names are quite strange, because these should be rarely-used functions anyway.
2019-01-17 18:11:48 +01:00
`tostring` converts its argument to a string value.
Explicit type conversions are rarely necessary in Terraform because it will
convert types automatically where required. Use the explicit type conversion
functions only to normalize types returned in module outputs.
Only the primitive types (string, number, and bool) can be converted to string.
All other values will produce an error.
## Examples
```
> tostring("hello")
hello
> tostring(1)
1
> tostring(true)
true
> tostring([])
Error: Invalid function argument
Invalid value for "v" parameter: cannot convert tuple to string.
```