Duplicate stdout to pipe into another command with named pipe in POSIX shell script function

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mkfifo foo
printf %s\\n bar | tee foo &
tr -s '[:lower:]' '[:upper:]'



This is a working POSIX shell script of what I want to do:

- printf %s\\n bar is symbolic for an external program producing stdout
- tr -s '[:lower:]' '[:upper:]' is symbolic for another command that is supposed to receive the stdout and do something with it
- tee duplicates stdout to named pipe foo

And the output is as expected:

bar
BAR

Now I'd like to tidy up the code so it becomes external_program | my_function. Something like this:

f() (
  mkfifo foo
  tee foo &
  tr -s '[:lower:]' '[:upper:]' 


But now there is no output at all.



                  
                  
                    
                      
                        
                        Asked by finefoot
                        (3554 rep)
                      
                    
                    
                      
                        
                        Mar 9, 2025, 01:34 PM
                        
                          
Last activity: Mar 9, 2025, 03:19 PM



            
            
              
              
    
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