The input to tsort can be provided as in this example:

$ tsort <<EOF
a b c
b c d e

If I have two files as inputs instead,




how can I provide the two files in bash as inputs to tsort ? Thanks.

closed as unclear what you're asking by muru, Thomas, mosvy, Isaac, RalfFriedl Nov 18 '18 at 0:06

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You need to put all entries of each file into a single line.

You can do so with an unquoted $(...) which will split on whitespace (and that includes newline) and then you can use echo on it to print the arguments into a single line.

This should work:

{ echo $(cat file1)
  echo $(cat file2)
} | tsort

This should produce the same output as your example does.

UPDATE: The input of tsort is broken on any whitespace, so preserving each file's contents in a single line isn't really important.

In that case, this should be enough:

cat file1 file2 | tsort

Though in your example, you don't really have a number of pairs, there is an odd number of items in your file1. As you noticed already, that is a problem for tsort.

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