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# Bash string manipulation cheatsheet
[https://gist.github.com/magnetikonline/90d6fe30fc247ef110a1](https://gist.github.com/magnetikonline/90d6fe30fc247ef110a1)
| **Assignment** | |
| :--- | :--- |
| Assign `value` to `variable` if `variable` is not already set, `value` is returned. <br> <br>Combine with a `:` no-op to discard/ignore return `value`. | `${variable="value"}` <br>`: ${variable="value"}` |
| **Removal** | |
| Delete shortest match of `needle` from front of `haystack`. | `${haystack#needle}` |
| Delete longest match of `needle` from front of `haystack`. | `${haystack##needle}` |
| Delete shortest match of `needle` from back of `haystack`. | `${haystack%needle}` |
| Delete longest match of `needle` from back of `haystack`. | `${haystack%%needle}` |
| **Replacement** | |
| Replace first match of `needle` with `replacement` from `haystack`. | `${haystack/needle/replacement}` |
| Replace all matches of `needle` with `replacement` from `haystack`. | `${haystack//needle/replacement}` |
| If `needle` matches front of `haystack` replace with `replacement`. | `${haystack/#needle/replacement}` |
| If `needle` matches back of `haystack` replace with `replacement`. | `${haystack/%needle/replacement}` |
| **Substitution** | |
| If `variable` not set, return `value`, else `variable`. | `${variable-value}` |
| If `variable` not set _or_ empty, return `value`, else `variable`. | `${variable:-value}` |
| If `variable` set, return `value`, else null string. | `${variable+value}` |
| If `variable` set _and_ not empty, return `value`, else null string. | `${variable:+value}` |
| **Extraction** | |
| Extract `length` characters from `variable` starting at `position`. | `${variable:position:length}` |
| Return string length of `variable`. | `${#variable}` |
| **Escaping** | |
| Single quotes inside a single quoted string. | `echo 'Don'\''t break my escape!'` |
| **Indirection** | |
| Return value of variable name held in `indirect`, else `value`. | `indirect="apple"` <br>`apple="fruit"` <br>`${!indirect-value}` |
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