Created
November 9, 2015 19:49
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Shell parameter expansion
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| #!/bin/bash | |
| # Use if unset or null | |
| echo ${x:-x} # x | |
| echo $x # | |
| # Assign if unset or null (only regular variables) | |
| echo ${y:=y} # y | |
| echo $y # y | |
| # Error if unset | |
| z= | |
| echo ${z?} # | |
| # Use if not null | |
| echo ${z+z} # z | |
| # Error if unset or null | |
| echo ${z:?} # parameter null or not set |
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