du: Print progress information to stderr

[des]

Summary

• On SIGINFO, print the current path to stderr rather than stdout.

• Do so immediately, instead of the next time we finish a directory.

• Document this behavior in the manual page.

PR: 296861
MFC after: 1 week
Fixes: d1588599c024 ("Report the next directory being scanned ...")

[wollman]

I haven't tested, but the code change looks good to me. I think the bit added to the manual page should be in a DIAGNOSTICS section, if you believe mdoc(7). (POSIX has a separate SIGNALS section but mdoc(7) doesn't suggest one.) I don't insist on this, though.

[des]

In D58702#1346970, @wollman wrote:

I think the bit added to the manual page should be in a DIAGNOSTICS section, if you believe mdoc(7).

I copied it from cp(1). Other manual pages including dd(1) and wc(1) have the same verbiage in roughly the same location.

[ziaee]

In D58702#1346997, @des wrote:

In D58702#1346970, @wollman wrote:

I think the bit added to the manual page should be in a DIAGNOSTICS section, if you believe mdoc(7).

I copied it from cp(1). Other manual pages including dd(1) and wc(1) have the same verbiage in roughly the same location.

No change requested, however I believe DIAGNOSTICS is correct for all of these. mdoc(7) is the reference manual, the sections are real standards, and organization is good.

[des]

In D58702#1347039, @ziaee wrote:

No change requested, however I believe DIAGNOSTICS is correct for all of these. mdoc(7) is the reference manual, the sections are real standards, and organization is good.

Well mdoc(7) says DIAGNOSTICS is for documenting error messages, which this isn't.