gdl output through nohup delayed

[brandy125]

I am used to spawn idl programs with nohup as:

spawn,"nohup idl <<< printloop &"

where printloop.pro could be

pro printloop

while 1 do begin
	print,systime()
	wait,1
endwhile

end

To keep it simple we do not need the spawn here. So I compare

nohup idl <<< printloop

with

nohup gdl <<< printloop

In the first case I get the time printed every second to the file nohup.out whereas in the second case it takes many seconds until a bunch of lines are being printed to nohup.out.

Where does this big difference come from? Why the output of gdl is soo slow compared to idl?

Anybody knows?

[slayoo]

Thanks for the report. I've just tried with freshly compiled gdl from the Github master branch and (trying out the simpler case without spawn):

• I get one output line every second (visible in the terminal)
• nothing is written to nohup.out (no such file is created)

Reading through nohup man page, I've noticed:

NOTE: your shell may have its own version of nohup, which usually supersedes the version described here. Please refer to your shell's documentation for details about the options it supports.

Which version of GDL, shell and nohup are you using?

[brandy125]

Thank you for verifying!
I tested on

GDL> !version
{
    "ARCH": "aarch64",
    "OS": "linux",
    "OS_FAMILY": "unix",
    "OS_NAME": "linux",
    "RELEASE": "8.2",
    "BUILD_DATE": "Jul 27 2022",
    "MEMORY_BITS": 64,
    "FILE_OFFSET_BITS": 64
}
GDL> !gdl
{
    "RELEASE": "1.0.1 Git",
    "BUILD_DATE": "Jul 27 2022",
    "EPOCH": 1658890800,
    "GDL_USE_DSFMT": 1,
    "GDL_USE_WX": 1,
    "GDL_POSIX": 1
}
GDL> 

and

GDL>  !version
{
    "ARCH": "x86_64",
    "OS": "linux",
    "OS_FAMILY": "unix",
    "OS_NAME": "linux",
    "RELEASE": "8.2",
    "BUILD_DATE": "Apr 21 2022",
    "MEMORY_BITS": 64,
    "FILE_OFFSET_BITS": 64
}
GDL>  !gdl
{
    "RELEASE": "1.0.1 Git",
    "BUILD_DATE": "Apr 21 2022",
    "EPOCH": 1650510000,
    "GDL_USE_DSFMT": 1,
    "GDL_USE_WX": 1,
    "GDL_POSIX": 1
}

The program /usr/bin/nohup comes from

coreutils-9.1-2.3.aarch64  or coreutils-8.32-8.5.x86_64

with

bash-5.1.8-2.1.x86_64 or bash-5.1.16-8.3.aarch64

Can I try anything else?

[GillesDuvert]

Is that a problem with GDL's readline facilities? Anyway, worksforme:
Below Mageia 8 (5.15.55-desktop-2.mga8) , looks good..

GDL> !version
{
    "ARCH": "x86_64",
    "OS": "linux",
    "OS_FAMILY": "unix",
    "OS_NAME": "linux",
    "RELEASE": "8.2",
    "BUILD_DATE": "Jul 13 2022",
    "MEMORY_BITS": 64,
    "FILE_OFFSET_BITS": 64
}

$ nohup gdl -e "while 1 do begin & print, systime() & wait,1 & endwhile"
nohup: ignoring input and appending output to 'nohup.out'
^C$ 
$ cat nohup.out 
% PREF_SET: Unknown preference: IDL_RBUF_SIZE
% PREF_SET: Unknown preference: IDL_MORE
Mon Aug  1 15:50:01 2022
Mon Aug  1 15:50:02 2022
Mon Aug  1 15:50:03 2022
Mon Aug  1 15:50:04 2022
Mon Aug  1 15:50:05 2022
Mon Aug  1 15:50:06 2022
Mon Aug  1 15:50:07 2022
Mon Aug  1 15:50:08 2022
Mon Aug  1 15:50:09 2022
Mon Aug  1 15:50:10 2022
Mon Aug  1 15:50:11 2022
Mon Aug  1 15:50:12 2022
Mon Aug  1 15:50:13 2022
Mon Aug  1 15:50:14 2022
Mon Aug  1 15:50:15 2022
Mon Aug  1 15:50:16 2022
Mon Aug  1 15:50:17 2022
% Interrupt encountered.
% Interrupted at: $MAIN$   

[brandy125]

Try to check the output of nohup.out in a second shell while the program is still running.
In my case the file is not updating until I press CTRL+C in the program. At this moment all lines appear in the nohup.out.

[GillesDuvert]

OK, sorry for the misunderstanding.
I would says that GDL 'print' does not flush the c++ ostream after write.

[brandy125]

Should/Could we change this behaviour?

[GillesDuvert]

solved in #1348

[brandy125]

Very nice! Works exactly as in IDL now!

Thanks!