Pipelines involving printf hang

[dspinellis]

The following command works fine.

dgsh -c 'echo hi | {{  cat & echo there & }} | cat'

The following command hangs.

dgsh -c 'echo hi | {{  cat & printf there & }} | cat'

[mfragkoulis]

The hang was due to the treatment of printf as a builtin.

That said the graph dgsh -c 'echo hi | {{ cat & printf there & }} | cat' is awkward because echo cannot provide multiple outputs.

dgsh -c '{{ echo hi & printf there & }} | cat' would be more appropriate.

However, the output is only hi if printf does not use a newline. The following works normally: dgsh -c '{{ echo hi & printf "there\n" & }} | cat'

[dspinellis]

Calling printf now works correctly even without a newline. Perhaps you didn't notice thethere before the prompt? (It would have been a serious problem if we treated newlines specially at this level.)

$ dgsh -c '{{ echo hi & printf there & }} | cat'
hi
there$

[dspinellis]

A few more things remain to close this.

• [x] Statements (e.g. dgsh -c 'echo hi | {{ cat & cat & }} | cat') should error, not hang.
• [X] We should also handle correctly other builtins that can cause trouble.
• [X] Ideally, we should just auto-wrap builtins when needed, rather than remove them. This will make it easier to integrate dgsh functionality into the bash distribution.

[mfragkoulis]

The graph dgsh -c 'echo hi | {{ cat & printf there & }} | cat' is totally legitimate and the handling is the expected; the command runs and terminates normally. Don't mind me, it was late last night :-) The graph dgsh -c 'echo hi | {{ cat & cat & }} | cat' is not allowed at the moment because of the presence of two flexible commands in a multiple block (we will revisit this in issue #4 -- multipipe blocks). The graph now exits with an error, it does not hang. Rephrased 1/3 and checked it.