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--cpu-prof-name 'CPU.${pid}.cpuprofile' doesn't replace the placeholder #57418
Description
Version
v22.13.0
Platform
Linux xps 6.8.0-52-generic #53~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Jan 15 19:18:46 UTC 2 x86_64 x86_64 x86_64 GNU/Linux
Subsystem
No response
What steps will reproduce the bug?
node -p process.pid --cpu-prof --cpu-prof-name 'CPU.${pid}.cpuprofile' && ls CPU*outputs
43689
'CPU.${pid}.cpuprofile'How often does it reproduce? Is there a required condition?
always
What is the expected behavior? Why is that the expected behavior?
Following the doc: https://nodejs.org/api/cli.html#--cpu-prof
If --cpu-prof-name is not specified, the generated profile is named CPU.${yyyymmdd}.${hhmmss}.${pid}.${tid}.${seq}.cpuprofile.
I expect to be able to use those placeholder when I specify a name, especially when I use the cluster module to avoid having all the profiling overriding each others.
I expected the filename to be CPU.43689.cpuprofile
What do you see instead?
'CPU.${pid}.cpuprofile'Additional information
No response
Activity
joyeecheung commentedon Mar 12, 2025
It looks like either a misunderstanding of what the doc says, or that the doc not being clear enough that the argument is not a pattern that will be filled by Node.js. The doc specifically says:
which is not to be interpreted as "if it IS specified, Node.js will fill in the blank using a user-provided pattern". Rather, it means "if it IS specified, the name provided will be used as-is".
joyeecheung commentedon Mar 12, 2025
labeling good first issue, I think it should be fixed by clarifying the docs that what's expected in the OP is not going to happen instead.
BourgoisMickael commentedon Mar 13, 2025
@joyeecheung could we have it as a feature to be able to use a pattern with placeholder in the name ?
Otherwise, using it with the cluster module, each process would overwrite the same file.
cecia234 commentedon Mar 13, 2025
@BourgoisMickael I was writing the docs and trying out the parameter myself. Calling
node --cpu-prof --cpu-prof-name 'CPU.${pid}.cpuprofile'I obtain the same output as you, but callingnode --cpu-prof --cpu-prof-name "CPU.${pid}.cpuprofile"(using double quotes) actually outputs a file with the pid in the name. Could you try it? Please note that I'm on windows at the moment.EDIT: after trying it on wsl, using double quotes I get a file with the name
CPU..cpuprofile, so the behaviour could be OS dependent.BourgoisMickael commentedon Mar 13, 2025
@cecia234 The
${}syntax is a parameter substitution/expansion in shell (https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html).Using double quotes or no quotes will trigger the substitution and replace it with the value of the variable
pidor an empty string.So on linux you end up sending
--cpu-prof-name CPU..cpuprofileto the process. Hence the use of single quotes to send the literal string${pid}as argumen without shell substitution.It doesn't seem like a big change to be able to handle pattern as name if it's already available when name is not provided
cecia234 commentedon Mar 13, 2025
Oof, I didn't know that I'm sorry.
I agree with you that it does not seem like a big change, I'll keep the docs PR open until a more experienced contributor will give some feedback.
jasnell commentedon Mar 13, 2025
I added the
feature requestlabel because it might actually be worthwhile exploring implementing this kind of replacement in the future. I agree that in the near term clarifying the docs is the best next step.6 remaining items
cli: clarify --cpu-prof-name allowed values
cli: clarify --cpu-prof-name allowed values
cli: clarify --cpu-prof-name allowed values
cli: clarify --cpu-prof-name allowed values
cli: clarify --cpu-prof-name allowed values
cli: clarify --cpu-prof-name allowed values
theanarkh commentedon May 10, 2025
You can submit an PR directly !
cli: support `${pid}` placeholder in --cpu-prof-name
cli: support `${pid}` placeholder in --cpu-prof-name
cli: support `${pid}` placeholder in --cpu-prof-name