New: fopen(3): Incorrect good practice suggestion
https://bugzilla.kernel.org/show_bug.cgi?id=215848
Bug ID: 215848
Summary: fopen(3): Incorrect good practice suggestion
Product: Documentation
Version: unspecified
Hardware: All
OS: Linux
Status: NEW
Severity: normal
Priority: P1
Component: man-pages
Assignee: [email protected]
Reporter: [email protected]
Regression: No
Hello!
From fopen(3):
"Therefore it is good practice (and indeed sometimes necessary under Linux) to put an fseek(3) or fgetpos(3) operation between write and read operations on such a stream."
I am not sure about the origin of this good practice but fgetpos(3) seems wrong. It has to be fsetpos(3) if I'm reading the C standard and POSIX[0] correctly.
BTW, calling fsetpos(3) will require a call to fgetpos(3) first. So why is it being advised as a good practice to call two functions (fgetpos and then fsetpos)? Maybe just i) mention fseek(3) only OR ii) mention fseek(3) and fflush(3) (instead of fsetpos(3))?
[0]
https://pubs.opengroup.org/onlinepubs/9699919799.2018edition/functions/fopen.html
Thanks!
Regards,
Avinash Sonawane (rootKea)
https://www.rootkea.me
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[Bug 215848] fopen(3): Incorrect good practice suggestion
https://bugzilla.kernel.org/show_bug.cgi?id=215848
--- Comment #1 from Avinash Sonawane ([email protected]) ---
I think we should only mention using fseek as a good practice between read and write operations since:
a. fflush can't be used on input stream i.e. if last operation was read while fseek() can be used between read-write or write-read.
b. fsetpos needs fgetpos to be called first. So let's drop fgetpos+fsetpos from the good practice suggestion
So I suggest this small change:
man3/fopen.3 +0 -2
@@ -138,8 +138,6 @@ result of writes other than the most recent.) Therefore it is good practice (and indeed sometimes necessary under Linux) to put an .BR fseek (3) -or -.BR fgetpos (3) operation between write and read operations on such a stream. This operation may be an apparent no-op (as in \fIfseek(..., 0L, SEEK_CUR)\fP
Thanks!
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[Bug 215848] fopen(3): Incorrect good practice suggestion
In reply to [email protected]https://bugzilla.kernel.org/show_bug.cgi?id=215848
Alejandro Colomar (man-pages) ([email protected]) changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |[email protected]
Resolution|--- |CODE_FIX--- Comment #2 from Alejandro Colomar (man-pages) ([email protected]) --- Hi Avinash,
I decided to keep fsetpos(3) to not lose the info, so I applied the following patch:
fopen.3: tfix
man3/fopen.3 +0 -0
@@ -114,7 +114,7 @@ Therefore it is good practice (and indeed sometimes
necessary
under Linux) to put an
.BR fseek (3)
or
-.BR fgetpos (3)
+.BR fsetpos (3)
operation between write and read operations on such a stream. This operation may be an apparent no-op
(as in \fIfseek(..., 0L, SEEK_CUR)\fP
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