Print from c++ file running on postgresql

Question

I am running some C++ code in postgresql. I am trying to print some output to keep track of the execution, but no result. Is there anything I need to add somewhere to enable printf command to work? I am adding the below mentioned files in my code:

#include "postgres.h"

#include <math.h>
#include <limits.h>
#include <inttypes.h>

What I am trying to print:

printf("abc");

Any help would be greatly appreciated, as I have been trying to get some output for the past 2 days. Thanks!

Edit : I am running the postgresql server using SSH. Let me know via comments if any more information is needed.

Nope. No output either. Is there any settings that have to be changed in postgresql to enable output to screen? — student001
– student001, Commented Apr 4, 2014 at 10:21
check /var/log/postgresql.log or a similar log file for the string abc... if you are running from a stored procedure, that's where the server log is going (probably)... — Massa
– Massa, Commented Apr 4, 2014 at 10:25

Craig Ringer · Accepted Answer · 2014-04-04 14:56:49Z

1

You need to use PostgreSQL's build-in logging system: http://www.postgresql.org/docs/current/static/error-message-reporting.html

From the reference:

elog(INFO, "count=%d", count);

The log level has to match the level you've configured PostgreSQL to write to its log file.

edited Apr 4, 2014 at 14:56

Craig Ringer

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answered Apr 4, 2014 at 10:22

Trygve Laugstøl

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1 Comment

Craig Ringer Over a year ago

elog is fine for debug tracing, etc. For production quality code that's meant to produce quality error messages, ereport is often preferable.

Lee Duhem · Accepted Answer · 2014-04-04 10:34:12Z

0

printf("abc"); will try to write to stdout, but normally Postgresql server runs as a daemon, which means it will close stdout, that is why you cannot see that string at the standard output.

You should use the error report facilities offered by Postgresql to output those message to Postgresql log file, as pointed out by @rygvis.

answered Apr 4, 2014 at 10:34

Lee Duhem

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1 Comment

Craig Ringer Over a year ago

Depending on the server startup, stderr (as opposed to stdout) often goes to the server log file. But it's much, much, much better to use elog and ereport.

I S · Accepted Answer · 2020-08-11 03:45:57Z

0

you can use fprintf(stderr, "abc\n"); instead of printf("abc");

answered Aug 11, 2020 at 3:45

I S

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