https://github.com/drone/envsubst

Go package emulates bash environment variable substitution
https://github.com/drone/envsubst

Last synced: 5 months ago
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Go package emulates bash environment variable substitution

• Host: GitHub
• URL: https://github.com/drone/envsubst
• Owner: drone
• License: mit
• Created: 2017-01-16T09:35:52.000Z (over 9 years ago)
• Default Branch: master
• Last Pushed: 2024-05-30T14:06:41.000Z (about 2 years ago)
• Last Synced: 2024-11-17T12:50:55.399Z (over 1 year ago)
• Language: Go
• Homepage:
• Size: 63.5 KB
• Stars: 273
• Watchers: 6
• Forks: 54
• Open Issues: 4
• Metadata Files:
  • Readme: readme.md
  • License: LICENSE

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README

          
# envsubst

`envsubst` is a Go package for expanding variables in a string using `${var}` syntax.

Includes support for bash string replacement functions.

## Documentation

[Documentation can be found on GoDoc][doc].

## Supported Functions

| __Expression__                | __Meaning__                                                     |

| -----------------             | --------------                                                  |

| `${var}`                      | Value of `$var`

| `${#var}`                     | String length of `$var`

| `${var^}`                     | Uppercase first character of `$var`

| `${var^^}`                    | Uppercase all characters in `$var`

| `${var,}`                     | Lowercase first character of `$var`

| `${var,,}`                    | Lowercase all characters in `$var`

| `${var:n}`                    | Offset `$var` `n` characters from start

| `${var:n:len}`                | Offset `$var` `n` characters with max length of `len`

| `${var#pattern}`              | Strip shortest `pattern` match from start

| `${var##pattern}`             | Strip longest `pattern` match from start

| `${var%pattern}`              | Strip shortest `pattern` match from end

| `${var%%pattern}`             | Strip longest `pattern` match from end

| `${var-default`               | If `$var` is not set, evaluate expression as `$default`

| `${var:-default`              | If `$var` is not set or is empty, evaluate expression as `$default`

| `${var=default`               | If `$var` is not set, evaluate expression as `$default`

| `${var:=default`              | If `$var` is not set or is empty, evaluate expression as `$default`

| `${var/pattern/replacement}`  | Replace as few `pattern` matches as possible with `replacement`

| `${var//pattern/replacement}` | Replace as many `pattern` matches as possible with `replacement`

| `${var/#pattern/replacement}` | Replace `pattern` match with `replacement` from `$var` start

| `${var/%pattern/replacement}` | Replace `pattern` match with `replacement` from `$var` end

For a deeper reference, see [bash-hackers](https://wiki.bash-hackers.org/syntax/pe#case_modification) or [gnu pattern matching](https://www.gnu.org/software/bash/manual/html_node/Pattern-Matching.html).

## Unsupported Functions

* `${var-default}`

* `${var+default}`

* `${var:?default}`

* `${var:+default}`

[doc]: http://godoc.org/github.com/drone/envsubst