Issues with running command in shell mode and piping inputs.

[ricka-hunt]

I'm trying to create a formatter for xan, a csv toolbox which contains a few useful csv formatting functions. They have this atomized design that encourages piping functions into each other.

Here's my current attempt at it:

return {
  meta = {
    url = "https://github.com/medialab/xan",
    description = "The CSV magician",
  },
  command = "xan",
  args = "fixlengths $FILENAME |xan input --trim |xan dedup",
  stdin = false,
}

And the log I get when trying to run it:

          2026-02-27 19:42:36[INFO] Run xan on /home/trickyni/Sync/2026-readlist.csv
          2026-02-27 19:42:36[TRACE] Input lines: { "#,book,Finised?,", "1,EIGHTYSIX- Vol.4,yes,", "2,  EIGHTYSIX- Vol.5,yes", "3,EIGHTYSIX- Vol.6,reading", "3,EIGHTYSIX- Vol.6,reading,", "2,EIGHTYSIX- Vol.7,yes,maybe", "3,,reading," }
          2026-02-27 19:42:36[DEBUG] Creating temp file /home/trickyni/Sync/.conform.4915938.2026-readlist.csv
          2026-02-27 19:42:36[DEBUG] Run command: { "/usr/bin/bash", "-c", "/sbin/xan fixlengths /home/trickyni/Sync/.conform.4915938.2026-readlist.csv |xan input --trim |xan dedup" }
          2026-02-27 19:42:36[DEBUG] Run default CWD: /home/trickyni/Sync
          2026-02-27 19:42:36[DEBUG] xan exited with code 0
          2026-02-27 19:42:36[TRACE] Output lines: { "#,book,Finised?,", "1,EIGHTYSIX- Vol.4,yes,", "2,  EIGHTYSIX- Vol.5,yes", "3,EIGHTYSIX- Vol.6,reading", "3,EIGHTYSIX- Vol.6,reading,", "2,EIGHTYSIX- Vol.7,yes,maybe", "3,,reading," }
          2026-02-27 19:42:36[TRACE] xan stderr: { "" }
          2026-02-27 19:42:36[DEBUG] Cleaning up temp file /home/trickyni/Sync/.conform.4915938.2026-readlist.csv
          2026-02-27 19:42:36[TRACE] Applying formatting to /home/trickyni/Sync/2026-readlist.csv
          2026-02-27 19:42:36[TRACE] Comparing lines { "#,book,Finised?,", "1,EIGHTYSIX- Vol.4,yes,", "2,  EIGHTYSIX- Vol.5,yes", "3,EIGHTYSIX- Vol.6,reading", "3,EIGHTYSIX- Vol.6,reading,", "2,EIGHTYSIX- Vol.7,yes,maybe", "3,,reading," } and { "#,book,Finised?,", "1,EIGHTYSIX- Vol.4,yes,", "2,  EIGHTYSIX- Vol.5,yes", "3,EIGHTYSIX- Vol.6,reading", "3,EIGHTYSIX- Vol.6,reading,", "2,EIGHTYSIX- Vol.7,yes,maybe", "3,,reading," }
          2026-02-27 19:42:36[TRACE] Diff indices {}
          2026-02-27 19:42:36[TRACE] Applying text edits: {}
          2026-02-27 19:42:36[TRACE] Done formatting /home/trickyni/Sync/2026-readlist.csv

If stdin = false it does not seem to make any changes, as shown in the logs.

If stdin = true, saving with ft_on_save on will overwrite all unsaved changes with a formatted version of the initial, pre-save file.

P.S. How does "append_args" work for shell mode? Xan has other tools that could be useful for formatting, but which shouldn't come by default.

Thanks!