Only if the output stream is 'stdout', because all JSON helpers like
print_string() only write on 'stdout'.

Supporting JSON is easy with the helpers. The biggest modification is to
extract the end value.

No behavioural changes intended for the moment, this is a preparation for a
future usage of print_timestamp() within a JSON context.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 lib/utils.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/lib/utils.c b/lib/utils.c
index 13e8c098..d7581709 100644
--- a/lib/utils.c
+++ b/lib/utils.c
@@ -1277,21 +1277,30 @@ int print_timestamp(FILE *fp)
 {
 	struct timeval tv;
 	struct tm *tm;
+	char ts[40];
 
 	gettimeofday(&tv, NULL);
 	tm = localtime(&tv.tv_sec);
 
 	if (timestamp_short) {
-		char tshort[40];
+		size_t len;
 
-		strftime(tshort, sizeof(tshort), "%Y-%m-%dT%H:%M:%S", tm);
-		fprintf(fp, "[%s.%06ld] ", tshort, tv.tv_usec);
+		len = strftime(ts, sizeof(ts), "%Y-%m-%dT%H:%M:%S", tm);
+		snprintf(ts + len, sizeof(ts) - len, ".%06ld", tv.tv_usec);
+		if (fp == stdout)
+			print_string(PRINT_ANY, "timestamp_short", "[%s] ", ts);
+		else
+			fprintf(fp, "[%s] ", ts);
 	} else {
 		char *tstr = asctime(tm);
 
 		tstr[strlen(tstr)-1] = 0;
-		fprintf(fp, "Timestamp: %s %ld usec\n",
-			tstr, tv.tv_usec);
+		snprintf(ts, sizeof(ts), "%s %ld usec", tstr, tv.tv_usec);
+		if (fp == stdout)
+			print_string(PRINT_ANY, "timestamp",
+				     "Timestamp: %s\n", ts);
+		else
+			fprintf(fp, "Timestamp: %s\n", ts);
 	}
 
 	return 0;

-- 
2.51.0

On Fri, 20 Feb 2026 19:54:02 +0100
"Matthieu Baerts (NGI0)" <matttbe@kernel.org> wrote:

> Only if the output stream is 'stdout', because all JSON helpers like
> print_string() only write on 'stdout'.
> 
> Supporting JSON is easy with the helpers. The biggest modification is to
> extract the end value.
> 
> No behavioural changes intended for the moment, this is a preparation for a
> future usage of print_timestamp() within a JSON context.
> 
> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>

I would go farther, fp is always stdout. Drop the argument to the function.

Hi Stephen,

On 21/02/2026 06:39, Stephen Hemminger wrote:
> On Fri, 20 Feb 2026 19:54:02 +0100
> "Matthieu Baerts (NGI0)" <matttbe@kernel.org> wrote:
> 
>> Only if the output stream is 'stdout', because all JSON helpers like
>> print_string() only write on 'stdout'.
>>
>> Supporting JSON is easy with the helpers. The biggest modification is to
>> extract the end value.
>>
>> No behavioural changes intended for the moment, this is a preparation for a
>> future usage of print_timestamp() within a JSON context.
>>
>> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
> 
> I would go farther, fp is always stdout. Drop the argument to the function.

Good idea!

To be coherent with the rest, I started to look at removing the same
argument from the caller functions, and similar ones. I did a very quick
draft with a few sed, etc. but I'm not sure whether I should take this
direction:

  https://github.com/matttbe/iproute2/commit/585b0109

WDYT? Or should I only drop fp from print_timestamp()? Or simply not use
it like it is done in many other helpers supporting JSON?

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.

Hi Stephen,

On 23/02/2026 14:20, Matthieu Baerts wrote:
> Hi Stephen,
> 
> On 21/02/2026 06:39, Stephen Hemminger wrote:
>> On Fri, 20 Feb 2026 19:54:02 +0100
>> "Matthieu Baerts (NGI0)" <matttbe@kernel.org> wrote:
>>
>>> Only if the output stream is 'stdout', because all JSON helpers like
>>> print_string() only write on 'stdout'.
>>>
>>> Supporting JSON is easy with the helpers. The biggest modification is to
>>> extract the end value.
>>>
>>> No behavioural changes intended for the moment, this is a preparation for a
>>> future usage of print_timestamp() within a JSON context.
>>>
>>> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
>>
>> I would go farther, fp is always stdout. Drop the argument to the function.
> 
> Good idea!
> 
> To be coherent with the rest, I started to look at removing the same
> argument from the caller functions, and similar ones. I did a very quick
> draft with a few sed, etc. but I'm not sure whether I should take this
> direction:
> 
>   https://github.com/matttbe/iproute2/commit/585b0109
> 
> WDYT? Or should I only drop fp from print_timestamp()? Or simply not use
> it like it is done in many other helpers supporting JSON?

I just sent a v2 with the minimal modifications around print_timestamp:
the argument is now simply ignored like it is the case in other helpers
supporting JSON. If there is a need to continue the cleanup, probably
better to do that in a different series I guess.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.