Can anyone guide me run an external command and get its return output? I failed with process_create: ?- process_create(path(ls), ['-l'], []). false.

Have you looked at the test cases for process_create/3 in test_process.pl ?

Which OS are you using? What do you get from this query: absolute_file_name(path(ls), Abs).

I am using Debian 10.6, swi-prolog 8.0.2. ?- absolute_file_name(path(ls), Abs). Abs = ‘/usr/bin/ls’.

Hmmm … it works for me on Ubuntu, SWI-Prolog 8.3.10. And presumably you get the same result with process_create('/bin/ls', [], [])? (or '/usr/bin/ls'). process_create/3 is documented as det, so it shouldn’t fail. I wonder if this works for you: process_create(path(echo), [hello], []). How about s…

I’ve just restarted the Prolog shell, and it gives me some different results: ?- process_create(path(ls), ['-l'], []). total 4 -rw-r--r-- 1 notooth notooth 106 Oct 28 08:30 test.pl true. ?- process_create(path(ls), [], [stdout(pipe(Var))]). Var = <stream>(0x55b96a953a40).

This looks normal. Wondering what could have caused a failure before the restart. I guess we’ll never know :frowning:

I put the code in test.pl file and run $ swipl test.pl. Then the shell caused that failure.

Tried this (file p.pl): :- initialization process_create(path(ls), ['-l'], []). Then in the shell swipl p.pl total 10084 drwxr-xr-x 2 janw janw 4096 Feb 12 2020 a -rwxr-xr-x 1 janw janw 8361 Apr 29 11:05 aa.pl -rw-r--r-- 1 janw janw 1528 Jun 5 2019 ac2_tests.P ... -rw-r--r-- 1 jan…

Note that @notooth is also using 8.0.2

Could indeed be an old bug. I don’t have 8.0.2 around. I’d need to rebuild it :slight_smile:

How to run external commands?

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How to run external commands?

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