parade: run multiple commands in parallel and coordinate their output.

Command line options

-h          print help
-b SIZE     use a SIZE-byte buffer for task reads (def. 4096)
-t COUNT    spawn at most COUNT tasks at a time (def. 10)

Each line of the command's input should be a shell command (to be processed by system(3)), optionally preceded by a name and a colon.

If any of the tasks exit with a non-zero status, parade will kill its child processes, halt, and return the same status code.

Example usage

cat <<HERE | ./parade
foo: command_that_prints 1 2 3 4 5
bar: command_that_prints $(range 1 1000)
baz: command_that_prints 10 20 30 40 50
command_that_prints 100 200 300 400 500
HERE

will spawn all the commands in parallel, yielding output like

command_that_prints 100 200 300 400 500: 100
command_that_prints 100 200 300 400 500: 200
command_that_prints 100 200 300 400 500: 300
command_that_prints 100 200 300 400 500: 400
command_that_prints 100 200 300 400 500: 500
baz: 10
baz: 20
baz: 30
baz: 40
baz: 50
foo: 1
foo: 2
foo: 3
foo: 4
foo: 5
bar: 0001
bar: 0002
bar: 0003
bar: 0004
bar: 0005
...