Comments (6)
Is this just to write the value? Use echo
for that.
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I want to write a shell function that returns a string, without printing it (very functional programming style). But it's not easy, as shell functions normally only return exit codes.
For FizzBuzz, I gave up, and had the fizz function go ahead and print the value instead of returning it. My Lisp senses are tingling, but whatcha gonna do...
from shellcheck.
Writing to stdout is how you return data from functions. The caller decides what happens to it, whether it's captured or merged with the caller's stdout. It's perfectly functional.
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Interesting. I suppose there are ways to redirect the output before/when the function is executed, so that the user doesn't see the string in the real STDOUT?
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Yes. you can capture/expand the data with variable=$(somefunction)
, pipe it with somefunction | otherfunction
, redirect it with somefunction > somefile
, and there are process substitutions and coprocs, and they can all be combined and nested arbitrarily.
In lisp/scheme, (+ 2 3)
will print 5 to the screen if you run it from a repl, but not if you use it as a sub-expression unless the function implicitly or explicitly returns it unmodified. That's the same thing.
There's no "real stdout" in bash, just like there's no "real return value" in lisp. There's just your own return value/stdout, and what the caller did with it.
from shellcheck.
Pipe |
! Genius!
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Related Issues (20)
- ShellCheck warning SC2320 triggered incorrectly in function arguments HOT 1
- Missing documentation HOT 1
- Bad advice, strange mapfile behaviour HOT 3
- ShellCheck does not recommend quote variables HOT 5
- Coalesce quotes with `shellcheck -p diff`
- Report spam in the wiki HOT 2
- Busybox sh and glob matching HOT 1
- ksh: Unexpected failure when using functions in arithmetic expressions
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- Wrong format string variables count
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- SC2164 HOT 2
- Associative array assignment with quoted keys triggers SC2079 HOT 1
- Writeable directory test passes with undefined variable HOT 6
- SC2206: Exception for integer variables HOT 1
- Feature Request: Partial runtime validator backed by Morbig for POSIX shell
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- QuickCheck-2.15 not accepted
- Disable directive ignored in array?
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