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enhance: clarify variable substitution more (#402)
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Co-authored-by: Easton Crupper <[email protected]>
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@wass3r @ecrupper
wass3r and ecrupper authored Apr 17, 2024
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Showing 1 changed file with 25 additions and 21 deletions.
46 changes: 25 additions & 21 deletions content/reference/environment/substitution.md
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Expand Up @@ -9,26 +9,30 @@ Vela imports a substitution library to provide the ability to expand, or substit

## String Operations

| Syntax | Description |
| ------------------------------- | ----------- |
| `${var^}` | var substitution with uppercase first char |
| `${var^^}` | var substitution with all uppercase |
| `${var,}` | var substitution with lowercase first char |
| `${var,,}` | var substitution with all lowercase |
| `${var:position}` | var substitution with substring |
| `${var:position:length}` | var substitution with substring and length |
| `${var#substring}` | var substitution with find and replace |
| `${var##substring}` | var substitution with find and replace |
| `${var%substring}` | var substitution with find and replace |
| `${var%%substring}` | var substitution with suffix removal |
| `${var/substring/replacement}` | var substitution with find and replace |
| `${var//substring/replacement}` | var substitution with find and replace |
| `${var/#substring/replacement}` | var substitution with find and replace |
| `${var/%substring/replacement}` | var substitution with find and replace |
| `${#var}` | var substitution |
| `${var=default}` | var substitution with default |
| `${var:=default}` | var substitution with default |
| `${var:-default}` | var substitution with default |
| Syntax | Example with Output | Description |
| ------------------------------- | ------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------- |
| `${VAR^}` | `VAR=example; echo ${VAR^}`<br>► `Example` | Converts the first character of the variable to uppercase |
| `${VAR^^}` | `VAR=example; echo ${VAR^^}`<br>► `EXAMPLE` | Converts all characters of the variable to uppercase |
| `${VAR,}` | `VAR=EXAMPLE; echo ${VAR,}`<br>► `eXAMPLE` | Converts the first character of the variable to lowercase |
| `${VAR,,}` | `VAR=EXAMPLE; echo ${VAR,,}`<br>► `example` | Converts all characters of the variable to lowercase |
| `${VAR:position}` | `VAR=example; echo ${VAR:1}`<br>► `xample` | Extracts a substring from the variable starting at the position |
| `${VAR:position:length}` | `VAR=example; echo ${VAR:2:3}`<br>► `amp` | Extracts a substring from the variable starting at the position with the specified length |
| `${VAR#substring}` | `VAR=exampleexample; echo ${VAR#exa}`<br>► `mpleexample` | Removes the shortest match of substring from the start of the variable |
| `${VAR##substring}` | `VAR=exampleexample; echo ${VAR##*exa}`<br>► `mple` | Removes the longest match of substring from the start of the variable |
| `${VAR%substring}` | `VAR=exampleexample; echo ${VAR%mple}`<br>► `exampleexa` | Removes the shortest match of substring from the end of the variable |
| `${VAR%%substring}` | `VAR=exampleexample; echo ${VAR%%mple*}`<br>► `exa` | Removes the longest match of substring from the end of the variable |
| `${VAR/substring/replacement}` | `VAR=exampleexample; echo ${VAR/exam/ap}`<br>► `appleexample` | Replaces the first match of substring with replacement in the variable |
| `${VAR//substring/replacement}` | `VAR=exampleexample; echo ${VAR//exam/ap}`<br>► `appleapple` | Replaces all matches of substring with replacement in the variable |
| `${VAR/#substring/replacement}` | `VAR=example; echo ${VAR/#exam/ap}`<br>► `apple` | If the variable starts with substring, replace it with replacement |
| `${VAR/%substring/replacement}` | `VAR=example; echo ${VAR/%mple/ctly}`<br>► `exactly` | If the variable ends with substring, replace it with replacement |
| `${#VAR}` | `VAR=example; echo ${#VAR}`<br>► `7` | Returns the length of the variable |
| `${VAR=default}` | `unset VAR; echo ${VAR=default}`<br>► `default` | If the variable is unset or null, it will be set to `default` |
| `${VAR:=default}` | `unset VAR; echo ${VAR:=default}`<br>► `default` | If the variable is unset or null, it will be set to `default` and the assignment is exported |
| `${VAR:-default}` | `unset VAR; echo ${VAR:-default}`<br>► `default` | If the variable is unset or null, it will be replaced with `default` without changing the value of `VAR` |

{{% alert title="Note" color="info" %}}
If you want to play with the examples above in a terminal, make sure you are in a `bash` shell.
{{% /alert %}}

### Escaping

Expand All @@ -45,4 +49,4 @@ steps:
+ - echo ${VELA_BUILD_COMMIT}
# This expression does escape the evaluation by adding the double '$$'
+ - echo $${VELA_BUILD_COMMIT}
```
```

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