substr

substr(str, offset, length) returns the portion of str starting at offset with at most length characters.

Signature

substr(str string, offset number, length number) string

offset is zero-based. A negative offset counts from the end of the string. Pass -1 for length to return everything from offset to the end of the string.

Example

Use the first 8 characters of a full commit SHA as a short identifier in Docker image tags:

variable "commit" {
  description = "Full git commit SHA"
  type        = string
}

computed "short_sha" {
  description = "Short commit identifier for image tagging"
  expression  = substr(var.commit, 0, 8)
}

task "build" {
  description = "Build and tag the image with the commit SHA"
  commands = [
    "docker build -t myapp:${computed.short_sha} .",
    "docker push myapp:${computed.short_sha}",
  ]
}

a3f9e21b4d6c8f12... becomes a3f9e21b.

Notes

offset and length count grapheme clusters, not bytes or code points.
If offset is beyond the end of the string, the result is an empty string.
If length exceeds the available characters from offset, the result is truncated to the string end.
Use length = -1 to extract from a position to the end: substr(str, 2, -1).

Overview

String

Number

Collection

Encoding

Crypto

Filesystem

Datetime

Regex

UUID

Conversion

Environment

Runtime

Signature

Example

Notes

​Signature

​Example

​Notes

Signature

Example

Notes