ERL-1299: file:pwrite/3 only accepts integer positions when used with ram files

[OTP-Maintainer]

Original reporter: JIRAUSER15707
Affected version: OTP-22.0
Fixed in version: OTP-23.1
Component: kernel
Migrated from: https://bugs.erlang.org/browse/ERL-1299

---

The documentation for [file:pwrite/3|http://erlang.org/doc/man/file.html#pwrite-3] lists limitations when using this function with "raw" files, but there are similar limitations when used with "ram" files.

For example, the function fails when given "eof"

{code:erlang}
Erlang/OTP 22 [erts-10.7.1] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe]

Eshell V10.7.1  (abort with ^G)
1> {ok, File} = file:open(<<"hello">>, [ram, write, read]).
{ok,{file_descriptor,ram_file,#Port<0.6>}}
2> file:pwrite(File, eof, <<" world">>).
{error,badarg}
3>
{code}

but works when given an integer position

{code:erlang}
Erlang/OTP 22 [erts-10.7.1] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe]

Eshell V10.7.1  (abort with ^G)
1> {ok, File} = file:open(<<"hello">>, [ram, write, read]).
{ok,{file_descriptor,ram_file,#Port<0.6>}}
2> file:pwrite(File, 5, <<" world">>).
ok
3>
{code}

Either the documentation should be fixed to report the limitations of using this function with "ram" files, or this function should be fixed to remove this limitation with "ram" files.

Thanks.

[OTP-Maintainer]

sverker said:

Documentation improved by

[https://github.com/erlang/otp/pull/2724]

 

[OTP-Maintainer]

sverker said:

Documentation fix scheduled for OTP-23.1